I thought the thread title said
ONE fighter?

Either my eyes are going bad, or most of you can't read that well...
My choice would be "RAZOR" Rob McCullough.
Just because I'm the driver of his bandwagon. That's my boy. I wanna see him up against some of the BEST LW's in this world. Kit Cope?

C'mon man...WTF.
Rob's Muay Thai striking, for the weight class he competes in...is HAAAAAARD to deal with, because it's so crisp, so fast, and does damage instantly. I don't see much of anyone testing him on the feet at 155. I could go on and on, but yeah, I wanna see him against guys like: BJ Penn, Sean Sherk, Tyson F'N Griffin, Roger Huerta & Nick or Nate Diaz...among others. Talk about FOTY candidates!

F-ck yeah.
Honorable Mention:
Mauricio Rua
Fedor Emelianenko
Rameau Thierry Sokoudjou
Wanderlei Silva