Ozzy Osbourne- a busk that sings awsome music for skooma, he will swear a lot.
noel and liam Gallagher. noel will play guitar while Liam will sing. they will argue a lot
david hasselfoff- kill him
tom cruise- the target of an assassination mission
opera - a woman in charge of an evil cult that should be killed
gabe newell- gives the player the crowbar, a rare and powerful weapon, if you ask for a second more powerfull crowbar then he shall promise you one within a short timeframe, but he will instead give it to you after a long delay. when asking for a third, uber crowbar, he will instead give you many, many hats.
most prosttutes will have the appearances of pop singers
ellis (from l4d2) working in a stable, with some crazy storys about some guy called kieth and the zombie apocalypse
gordon freeman- a completely silent man
captain price- a man speaking in a well exhadurated english accent, he will die
i made this list on short notice, please expand it