PBF vs Pacman (present) if only Floyd was still hanging around the lightweight division! Floyds power was amazing at that weight so they'd be pretty evenly matched in that sense. I think Floyds other advantages would have been too much for Pacman but we'll never know

Eubank vs Mclellan
Hamed vs Floyd (Floyd called him out after Coralles..would have been interesting)
Cotto vs Tzsyu (2005..Tzsyu exposes Cotto)
Margarito vs Floyd (Just for everyone to STFU about margarita!)