This is tough. I voted Andy though. I just love his CSM sculpt. It is probably one of the most accurate 1:6 sculpts of all time. Definately under appreciated.
Trevor is probably my favorite current sculptor. He is doing some amazing stuff right now, and just as good as Andy.
Dooley! Where the heck has he been? The last thing I remember him doing was Jabba! He is the best at the modern horror, gory stuff hands down. Although Matt is giving him a run know with 805.
Oluf is THE Universal Monster go to guy. Without him, I probably woudn't be here today because he sculpted the first 12" Frankenstein figure, which introduced me to Sideshow. Not nearly enough work from him recently either.