I've made a fair few. Though my older flags are forever lost, here's the new ones I've done.
Penguin Dictators (my main nation)
In think this is still a favorite of mine, and not just because it ended up winning 10KI's Best Flag Contest. But I've always just really liked the look of it compared to my other work.
Colorful Crows (my 10KI nation)
This was my first flag that I made with Ibis apainter X (what I use for all my flags) that I still have a fondness for.
Crow Metropolis (my Thalassia nation)
This I believe was my third project, and my second favorite flag right behind Penguin Dictators.
Dead Bodies Everywhere you Go (puppet nation)
Project number 4, although I'm still pretty meh with this one. If anything it looks more like part of a book cover than a flag.
The Seven Levels of Heaven (puppet nation)
Project number 5. Even though it's far from what I was going for, I still am a little fond of it. That being said I'll be revamping it soon to fit more of what I was originally wanting.
Toucan Samgu (Puppet nation)
My latest (7th) project (6th was Hapi's flag). This one was more of a joking-ish one made when I decided to create this nation a couple of days ago. I might change it down the road to something more serious since I have no real attachment to this one, but we'll see.
My next projects are for my two other joke nations: The Popping Purple Populacy of the Peppy Peaceful People of Pepperton, and The (currently until I can change it) Allied States of the Bionic Blue Beatles of Beaverton.
Update:
The Peppy Peaceful People of Pepperton
I specifically uploaded the ripple version because actually looks 10x better with it. I chose purple as the main color due to the moniker being "The Popping Purple Populacy"