Okay, since I just spent faaaaar too long looking for them and only finding one, here are some
aliases associated with Bobby Singer .
Episode 4.14
FBI - Mike Kayser
(Used over phone when Sam and Dean's cover story is checked.)
Episode 5.15
Health Department - Lou Dunbar
Police - Pete Lovell
CDC - Frank Castle
FBI - Tom Willis (ETA: he uses this name in the episode)
Federal Marshall - Bill (???er)
(Labels on the phone bank at Bobby's, can't quite make out the one on the end.)
>(ETA: I made a clearer screencap, click for larger)
Anybody know of any clarifications or any others that have been used or referenced on the show, shout 'em out. :-)