Reu's Dragon Claw was way ahead of it's time and no doubt one of the coolest Mugen OC's of that time period.
If I had to choose between his Evil Ryu or Ken, it's Evil Ken no doubt. Not only that we got the best Evil Ken at the time but something about Evil Ken is badass. His winposes are cool especially the ones where Bison taunts him with Evil Ken retaliating or the one where the "Satsui No Hado" releases and Ken faints at the end. His COME ON! taunt is pretty cool too.
Gordeau is easily my #1 pick since he's one of the most fun characters I ever played as in recent years. In fact, using him did made me a Gordeau main in UNICLR.
Since I can vote for up to four, my other favorite characters of his include Piranha Plant, Dedede, and Adachi. For Plant and Dedede, the way they both look and play really impressed me. As for Adachi, due to how well made he is shows that we can definitely see the DLC characters from Arc Sys and other anime fighting games free of charge. xD