Well, I've never really completed a game, so I don't really have any "complete" characters or enemies...not really.
BUT...one of the first characters that comes to mind is Alisha.
She's from my very first RPG, in RPG Maker (PS1).
She started out as a half-vampire witch or something, she was kind of a ripoff of Marivel from Wild ARMs 2. But, for some reason, whenever I decided to try drawing all the characters from that game, I never liked drawing...her clothes. I was bad at drawing robes and witch hats! So she was often nude, just 'cuz. That's probably what led me to make her a succubus. But, she's kinda half-vampire half-succubus, I guess. And she doesn't wear clothes. And she hates men. And...she's a lesbian. She even makes advances on the fairy girl. She also has some kind of hair powers, using her hair as wings, weapons, and taking shape of some kind of large monster mount. She's a really random somewhat ridiculous character, but that's what makes her so fun.
Some other heroes of mine that I'm particular fond of...a dwarf, from the same game as Alisha. There's nothing really outlandish about him, he's just a mainly bearded, armored, axe-wielding dwarf. But that's why I like him I guess. When I think of "crossovers" with my own characters, he's usually one of my first choices. Also, a character named Pumpkin, from a different game...idea. She's never been in an actual project at all, but she was one of those characters that was always fun to draw. She's almost as ridiculous as Alisha though.
There's also my pseudo-mascot characters, Lucent, and Bogi. But I'm not gonna say anything about them yet...
As for enemies...hmmm. Drawing a blank here...I've only ever used my own art for enemies in 2 projects, out of all this time...One enemy I like is called a Tiger Ball. Picture a Rabite from the Mana games, but with tiger features!
As for antagonists, let's go with one that's actually in a project, let's see...I don't know if I've ever even done that! Sheesh!
Okay, here's one from one of my ideas, well the game he was to appear in is started, but there's not much there. He's an alien from another world. He's captured several humans, without leaving a trace, or even with demands. Why did he capture them? Because his world is on the brink of destruction, and he needs the best minds from your party's home planet to save it! Well, it's actually a big gamble, because his technology is more advanced, but it's...different. Different resources, different climate, different goals...it all points to a solution. After you defeat him, you discover a solution, and even offer to help. He accepts, but declares he will help your planet, because you help his, and he owes you. He has drastic methods, but he never KILLED anyone, so...he basically accepts some extreme "community service" for his efforts. He still messed some things up, separating families and such, but he's not EVIL. Still an antagonist to you.
Then again, I never fully decided his entire story. No name either, like the main cast of that game. It was supposed to be a simpler project too.