Would have to say.... Bioshock series: Good ol' bloody fun and ambient eeriness. Red Dead Redemption: GTA with horses. Nuff' said! Oh and good story too. S.T.A.L.K.E.R. series: Large open zones, blowouts, mutants, scary, etc. etc. Amnesia: Although I can't beat it damn is it scary!
I don't have any pictures but I'll never forget when my fathers mouth hit the floor when i learned the combos and specials in the original Mortal Kombat and finally beat him haha.