Guys that haven't played in a long time like Levi and Drex were incredible in their day. Too many to list in that department, the Wldthngs and so on like that.
Many of the current muppets listed or otherwise. Guys like Lazerr, AckAck, so many others. Bruv and a number of The Few. Some of the current Top Gun guys. Joe a Cheem and Drboner. Dolby and his Cardigan.
Batfink has a great point too, anyone willing to fight and has a good attitude = a good pilot, or at the very least has the potential to be a good pilot.
One guy I haven't seen listed that should be, IMO, is Fester. That guy isn't just a good pilot, he's good at every facet of the game. I think he got nearly all the achievements HTC created before he stopped flying recently, or came closer than anyone. Any challenge out there, he seems to attack it and master it within the game. I can think of only a very very select few other pilots that are such expert/Beasts like Bruv puts it, in every facet of the entire game, be it ACM fighting or whatever else.
I would like to see one of these "list" threads for "best accomplishments" or some such. I still think that video Grizz made of the 99 262 kills is probably the best and hardest to replicate feat I've seen in 15 years here now. I honestly can't think of anything to top that, and it still makes me laugh watching it. I know there are others that are impressive, but I've never seen anyone match that streak, and doubt I will.