Oppainter, sysfailur, JCviggen, & MrIcee are well known to me as crazy extreme overclockers (insane phase change, TEC+water, and hardware mods). I think all are affiliated in some way with
www.xtremesystems.org. I KNOW all are always found somewhere near the top of 3dmark rankings and have been for a long time now.
Player0 was unknown to me before that thread about his RBX review on the forums but I believe he is also a fairly well known pelt+water extreme overclocker.
Other people I just don't know.
Honestly we aren't extreme overclockers here by and large. I am fairly extreme in hardware modification when required but I'm still using a GF3 in my gaming box so I am not about to break any 3dmark records. I DO know a fair amount about testing and heat transfer theory though...