I've got a few.
Tekken:
First and foremost, I love Yoshimitsu. He's been my main character throughout the entire Tekken series. That is, until Tekken 6 came around and fucked his moveset. I went from being godlike to fairly decent. I do not like this, because now he's my third best character.
Then there's Jin Kazama (post-Mishima Style Karate unlearning). He became my second in Tekken 5 and remains my second best today.
Finally, Lars Alexandersson. I didn't expect my best fighter to be the newest of the new, but whatever. He's got a great moveset and an interesting story, as well as a distinctive appearance.
Street Fighter:
Ryu (therefore, Ken as well), for obvious reasons. Frankly, who is an avid fan of Street Fighter is probably good with him.
My favorite Street Fighter character, though, is by all means Vega. When Street Fighter IV came out and I got to learn his moves (and after I modded my 360 controllers so they would have shit D-pads), I stuck to Vega like protein-based stains on the dress of a White House intern. He's a glorious bastard with a simple yet fantastic design and an awesome moveset. He also reminds me of Narcist Prince from Super Punch Out, which is cool.