I'm going to bend the rules here - I have multiples on this one, and fortunately I've already written about most of them. I'll limit it to three:
- The AD&D ranger I ran up to high level is discussed here
- My favorite Gamma World character is here
- My favorite Mechwarrior character is here
A somewhat sad note is that no, I haven't played any of them since I wrote those posts. I don't really expect to, since they are mostly from older editions of games, but it could happen someday. Also, I haven't played much at all in the last 15 years or so as I've been almost 100% on the DM side of the table. I have managed to play a few sessions of D&D 4E and I'm playing a cavalier in a friend's Pathfinder campaign right now and that's been fun but it's a rare thing for me.