After playing through GTA 4 again for the first time since it came out, I was thinking it would be awesome if Rockstar revisited it and made a zombie DLC for it like the Undead Nightmare for Red Dead. I know they won't, seeing as they are working on Agent and L.A. Noire. But even so, it would be awesome.
It'd be cool to see some of the characters in zombie form, or fighting to survive. The way I imagine it is similar to an 'I Am Legend' sort of vibe. Deserted streets, with hordes of zombies waiting to pop out and ravage you. Would be awesome.
Thought I'd throw it out there as a topic. ^^