1. Maryland. Let's get this out of the way: I have biases. But honestly, Maryland is the best example of how to do this flag thing right. Distinctive colors in a catchy pattern that dates back to traditional heraldry. This flag is so rad that the state has actual rules on what should be at the top of the flagpole (a gold cross bottony). (Didn't know the word "bottony?" Now you do. Use it in scrabble.) Anecdotally/being from there, I can tell you that I've seen a lot of Maryland state flag tattoos. Can your state flag boast the same?
2. Wyoming. See previous note about bias. But seriously, there is a fucking bison on this flag. I dare you to do better.
3. California. Placing 3rd below Wyoming only because a bear is a slightly more predictable mascot choice than a bison.
4. Alaska. Simple and recognizable, this is an astronomer's dream flag. It is definitely incredibly cool, and the backstory is pretty neat too. Maybe you'd deduct some points because Ursa Major + north star are not Alaska-specific (more like Northern Hemisphere-specific, which isn't specific at all), and also see my earlier thoughts about bears...but really, this flag is beautiful.
5. New Mexico. This is one state that could give the other states a run for their money in the "percentage of residents with this tattoo" competition. It's only rated so low because I think if you asked most New Mexicans what they'd put on the flag if they had the choice, they'd say green chile first and then list the Zia sun symbol second. Also, fun fact — one of only four state flags not to include blue! Maryland, California, and Alabama are the others. The lesson here is if you want a distinctive state flag, maybe skip the duh choice of blue.
6. Arizona. I find this one to be a little over the top, but then, so is Arizona.
7. South Carolina. I hedged on putting this on here, but as someone who likes plants very much, I have to throw down for them on account of them choosing to feature the palmetto.
Honorable mentions: Yeah yeah Texas is ok. Tennessee: also looking good because, while the colors are predictable, the geometry is interesting. Ohio gets points for being a weird shape. Alabama is simple and distinctive.
Pre-emptive nopes: I hate the Colorado state flag. If you don't hate it, fine, but you're wrong. It looks like bad 70s design and, more importantly, people emblazon it EVERYWHERE as soon as they move there. Also, I am uncomfortable with Hawaii's inclusion of the Union Jack.
All the other flags are boring and stupid.