Zombie mode.

[lew!]

You can be a zombie in GTA4, Not sure if you can on xbox..
But when you create your character for multiplay, if you press L1 you get the zombie costume.

There are many theorys behind this.. Some say you have to be killed by a rockstar dev, or kill a rockstar dev, or have certain acheivments.

I got it..
http://kezins.com/wp-content/uploads/2008/05/img00206.jpg

[Neil]

Yea www.gta4.net has a thing about it, looks quite good, my guess is that's PS3 only, haven't heard anything from 360 users so it must be something from Rockstar because of the exclusive DLC for 360 or something, some people say you get it when you reach rank 10 but apparently a rank 2 guy has it so that may not be true xD

[lew!]

Im rank 1 :P
TBH i think it has something about killing someone..

ACTUALLY, BRAINWAVE:::
Mabye if its that you get killed so many times in one game, you get it? Because zombies are dead.. if you get killed then ur dead, so if you get killed a lot, then you could unlock it?