Whith just main characters, I'm not so good at finding the #1 stereotype. But GROUP stereotypes? That's where the real money is. I guarantee you that most comics/movies/anime/anything that has a semi-large group of main and secondary characters will have, if not all, MOST of the personalities I listed below. Some characters even have two, or three.
Here's the list:
1) The dense, "shoot first and ask questions later" character. (often in the form of the inexperienced hero)
2) The smart character who is always either really short, really tall, or ironically sexy.
3) The quiet character who most likely has a tragic past.
4) The "cute" character who has no real purpose other than being cute. Occasionally freakishly strong for comedic purposes.
5) The character who has their smart moments, but is usually dense and always obsessed with the opposite gender. (or just one person of the opposite gender)
6) The character who gets angry very, very easily, and usually takes it out on whoever angers them. (or tries to)
7) The bubbly character, usually female, a very effeminate male, or of unknown gender, who just NEVER STOPS BEING HAPPY until it comes time for a major plot twist, wherein they suddenly become serious for the duration of the twist, then return to being HAPPY ALL THE TIME.
The other "cute" character who isn't humanoid in any way. (the "mascot" character)
9) The gratuitous "sexy" character for fanboys (or girls, depending on the character's gender) to gawk at. comes in two varieties:
---9.1) The gratuitous "sexy" character who is very naive and/or innocent, and doesn't realize they're sexy.
---9.2) The gratuitous "sexy" character who is in no way naive, and flaunts their sexiness constantly.
10) The character who THINKS they are the gratuitous "sexy" character, but really isn't.
There's more, obviously, but that's my top ten. And by that I mean, the first ten that came off the top of my head. (ohoho pun!)
Also, for your future reference Cassi, it's spelled "character."