Donetsk Republic (proposed), since the 1990s
This is the other flag that’s been flying around Donetsk lately, and it too predates the current crisis. The colours are clearly based on the Russian model, but they’re given different meanings. Black for coal, blue for the Sea of Azov, and red for the memory of the 1918 Donetsk-Krivoy Rog Soviet Republic.
Wikipedia identifies a plain version of this tricolour as the flag of the that short-lived state, but as far as I know the flag was invented in the 90s. I can’t find any evidence of this flag being used as far back as 1918. And when you think about it, it wouldn’t really make sense. Why would a Soviet Republic use a flag based on the old Russian tricolour instead of a red flag? Why would the red stripe represent Donetsk-Krivoy Rog if the entire flag was based on that old republic’s flag?
Weirdly, the emblem on the shield in the centre of the flag is the Archangel Michael, which is most famously the emblem of Kiev. It’s weird how all the separatist flags have Ukrainian symbols embedded within them.

Donetsk Republic (proposed), since the 1990s

This is the other flag that’s been flying around Donetsk lately, and it too predates the current crisis. The colours are clearly based on the Russian model, but they’re given different meanings. Black for coal, blue for the Sea of Azov, and red for the memory of the 1918 Donetsk-Krivoy Rog Soviet Republic.

Wikipedia identifies a plain version of this tricolour as the flag of the that short-lived state, but as far as I know the flag was invented in the 90s. I can’t find any evidence of this flag being used as far back as 1918. And when you think about it, it wouldn’t really make sense. Why would a Soviet Republic use a flag based on the old Russian tricolour instead of a red flag? Why would the red stripe represent Donetsk-Krivoy Rog if the entire flag was based on that old republic’s flag?

Weirdly, the emblem on the shield in the centre of the flag is the Archangel Michael, which is most famously the emblem of Kiev. It’s weird how all the separatist flags have Ukrainian symbols embedded within them.

Brunei, since 1959
I’ve always thought the hands on this flag kind of look like they’re shrugging. Like “I dunno, have a parasol I guess.”
Brunei is one of only two countries in the world to have a yellow background on their flag. (The other one is Niue.)

Brunei, since 1959

I’ve always thought the hands on this flag kind of look like they’re shrugging. Like “I dunno, have a parasol I guess.”

Brunei is one of only two countries in the world to have a yellow background on their flag. (The other one is Niue.)

Georgia, 1990-2004
I always thought Georgia’s old flag was better than its current one. The colour scheme and the composition were so unique, even though it was such a simple flag. The flag was based on the one used by Georgia from 1918 to 1921, which was basically the same except for its wider ratio.
(designer: Iakob Nikoladze)

Georgia, 1990-2004

I always thought Georgia’s old flag was better than its current one. The colour scheme and the composition were so unique, even though it was such a simple flag. The flag was based on the one used by Georgia from 1918 to 1921, which was basically the same except for its wider ratio.

(designer: Iakob Nikoladze)

Tobago (proposed), 1977
Red represents the blood shed by slaves, black represents the country as a whole, and green represents nature. In the centre is a map of Tobago in gold, with the island’s motto beneath it.
Gotta say Tobago, Trinidad’s got you beat on this one.
(designer: Claudette Hector Daniel)

Tobago (proposed), 1977

Red represents the blood shed by slaves, black represents the country as a whole, and green represents nature. In the centre is a map of Tobago in gold, with the island’s motto beneath it.

Gotta say Tobago, Trinidad’s got you beat on this one.

(designer: Claudette Hector Daniel)

Maryland, 1904
Happy Maryland Day! The state of Maryland has the fanciest, most heraldic flag in the Union. It’s based on the coat of arms of George Calvert, the 1st Baron of Baltimore, but as a flag it has its origins in the Civil War.
In the 1850s the black and yellow Calvert family arms started being flown as the “Maryland colors” at public events. In 1861, secessionists started flying the red and white Crossland family arms, and Confederate soldiers from Maryland decorated themselves with the cross bonny symbol. In the 1880s, the two symbols started being flown together on flags that looked much like the current state flag (although the Crossland banner was often in the 1st and 4th quarters instead). In 1904 the state flag was officially adopted.

Maryland, 1904

Happy Maryland Day! The state of Maryland has the fanciest, most heraldic flag in the Union. It’s based on the coat of arms of George Calvert, the 1st Baron of Baltimore, but as a flag it has its origins in the Civil War.

In the 1850s the black and yellow Calvert family arms started being flown as the “Maryland colors” at public events. In 1861, secessionists started flying the red and white Crossland family arms, and Confederate soldiers from Maryland decorated themselves with the cross bonny symbol. In the 1880s, the two symbols started being flown together on flags that looked much like the current state flag (although the Crossland banner was often in the 1st and 4th quarters instead). In 1904 the state flag was officially adopted.

Ghana, 1957-1964, since 1966
Happy independence day, Ghana. You’ve got a damn nice flag.
(designer: Theodosia Salome Okoh)

Ghana, 1957-1964, since 1966

Happy independence day, Ghana. You’ve got a damn nice flag.

(designer: Theodosia Salome Okoh)

Portuguese, Spanish, and New Zealand Olympic Teams, 1980

As part of the US-led boycott of the 1980 Moscow Olympics, three countries participated under their Olympic Committee’s flag. While Spain and Portugal incorporated elements from their national flags, New Zealand went with the silver fern.

Araucania

The tricolour on Araucania’s current flag [top] may be unremarkable, but that coat of arms is damn slick. This proposal from around 2006 [bottom] on the other hand just looks kind of sickly.

Cape Breton Island
This is one of several unofficial flags, but it’s the most common one you’ll find on the island. 

Cape Breton Island

This is one of several unofficial flags, but it’s the most common one you’ll find on the island. 

Jaffna (spurious)
Wikipedia, in typical Wikipedia fashion, incorrectly identifies this as the flag of the Jaffna kingdom, a Tamil state on Sri Lanka that was conquered by the Portuguese in the early seventeenth-century. In fact, this is a modern flag used by a pretender with a dubious claim to that non-existent throne who lives in the Netherlands and is most well-known for appearing on some dumb British reality show.

Jaffna (spurious)

Wikipedia, in typical Wikipedia fashion, incorrectly identifies this as the flag of the Jaffna kingdom, a Tamil state on Sri Lanka that was conquered by the Portuguese in the early seventeenth-century. In fact, this is a modern flag used by a pretender with a dubious claim to that non-existent throne who lives in the Netherlands and is most well-known for appearing on some dumb British reality show.

Nauru Pacific Line
This flag was originally misreported as Nauru’s civil ensign, probably because it prominently features the national flag’s twelve-pointed star. In fact, it’s the house flag of Nauru’s national shipping line.

Nauru Pacific Line

This flag was originally misreported as Nauru’s civil ensign, probably because it prominently features the national flag’s twelve-pointed star. In fact, it’s the house flag of Nauru’s national shipping line.

New Zealand (proposed)
Prime Minister John Key wants to have a referendum on changing the national flag. His preference is a black flag with a silver fern on it, which would would look something like the above image. The current blue ensign has been around for quite some time (since 1869), but the silver fern is pretty old itself. It was being used as a national symbol at least as early as the Second Boer War.

New Zealand (proposed)

Prime Minister John Key wants to have a referendum on changing the national flag. His preference is a black flag with a silver fern on it, which would would look something like the above image. The current blue ensign has been around for quite some time (since 1869), but the silver fern is pretty old itself. It was being used as a national symbol at least as early as the Second Boer War.

East African Community, since 2009.
The stripes on the EAC’s flag reflect the flags of all of its three original member states: Kenya, Tanzania and Uganda. The blue stripes also stand for Lake Victoria, which is shared between the three countries.
The original flag was adopted on 1997, but the seal in the centre was updated when Burundi and Uganda joined in 2009.

East African Community, since 2009.

The stripes on the EAC’s flag reflect the flags of all of its three original member states: Kenya, Tanzania and Uganda. The blue stripes also stand for Lake Victoria, which is shared between the three countries.

The original flag was adopted on 1997, but the seal in the centre was updated when Burundi and Uganda joined in 2009.

Denmark (mourning flag), until 1743
Flying a flag at half mast hasn’t always been the main sign of mourning. In Denmark they used to fly a black version of the national flag.

Denmark (mourning flag), until 1743

Flying a flag at half mast hasn’t always been the main sign of mourning. In Denmark they used to fly a black version of the national flag.

Turkmenistan (proposed), 2004
The Agzybirlik movement has made a bunch of proposals for the flag of a Democratic Turkmenistan. Someone on FOTW helpfully translated their description:

The theme of the flag is simple and dear to the heart of every Turkmen: scarlet and green (al-yashyl)-are always associated by the Turkmen with abundance and welfare, these colors are the the symbols of triumph, kindness and justice. 
Black color-reminds us of hard times being the share of our nation, about the tests trying the existence of the Turkmen Nation. And the disc of sun on the flag is the symbol of the richness of our soil and the source of life. There are other historical parallels to the choice of these three colors: 
Red-connected with the Communist history of the country which saw the founding of the modern state of Turkmenistan. 
Green- is connected with Islam, the religious faith of the nation. 
Black-the color of the flag of the Medieval Turkmen state, suggesting the symbolic continuity of Turkmen statehood. 

At the same time this flag was on their website, they had another tricolour with red-green-white stripes. No explanation for that one. Around 2006 they changed their proposal to one with just the red and green stripes and the sun disc.
This would certainly be a more conventional design but I actually think it would be a step down. Turkmenistan’s flag may be complicated as heck, but it’s unique and it has character and it genuinely reflects a local artistic tradition. The proposed alternative is kind of just one more tricolour in someone else’s colour scheme.

Turkmenistan (proposed), 2004

The Agzybirlik movement has made a bunch of proposals for the flag of a Democratic Turkmenistan. Someone on FOTW helpfully translated their description:

The theme of the flag is simple and dear to the heart of every Turkmen: scarlet and green (al-yashyl)-are always associated by the Turkmen with abundance and welfare, these colors are the the symbols of triumph, kindness and justice. 

Black color-reminds us of hard times being the share of our nation, about the tests trying the existence of the Turkmen Nation. And the disc of sun on the flag is the symbol of the richness of our soil and the source of life. There are other historical parallels to the choice of these three colors: 

Red-connected with the Communist history of the country which saw the founding of the modern state of Turkmenistan. 

Green- is connected with Islam, the religious faith of the nation. 

Black-the color of the flag of the Medieval Turkmen state, suggesting the symbolic continuity of Turkmen statehood. 

At the same time this flag was on their website, they had another tricolour with red-green-white stripes. No explanation for that one. Around 2006 they changed their proposal to one with just the red and green stripes and the sun disc.

This would certainly be a more conventional design but I actually think it would be a step down. Turkmenistan’s flag may be complicated as heck, but it’s unique and it has character and it genuinely reflects a local artistic tradition. The proposed alternative is kind of just one more tricolour in someone else’s colour scheme.