1. P.O.T.S- All of his characters that attracted me to mugen first before i started. His Geese, Ryu, and Cammy really caught my attention amongst the rest.
2. Jmorphman- His characters are what caught my attention. His Kyo, and Joe really caught me. Next to his Ryo as of now. I love all of his characters.
3. Vyn- I kinda like the focus style attack he did with his Rock, Terry and Rugal.
4. Dr Kohaku- all of his characters are just amazing. Especially the cvs styled ones he did. His Nanaya is my favorite one next to Kohaku and White Len.
5. Rajaaboy- No comment. Just Rajaaboy... Pure awesomeness.
6. Ikaruga- Like you said, his characters can be very challenging if you want competition against them.
7. Infinite- That dude has come a long way man, his characters are top notch. especially his Deadpool, Kain, and Billy. He's put in a ton of work on those characters. Hope to see him return with a new character again very soon. :)
Basically, i like the pots/jmorphman styled characters in the mugen community.