I have pre-ordered several games through there but the only bonuses that were really worth it, so to speak, were the ones that came with Mass Effect 2 . The heavy weapon, It fires flaming black holes that drag enemies out from behind cover and incinerate them. Fire that bad boy down a crowded hallway . . . it's fucking bad-ass . . . it's not even fair. I love it!
Other than that I can't think of a pre-order bonus that made me really, extra, happy but I pre-order anyway because I want to make sure I get a copy and, most of the time, that does it. I also like the little bits of free swag they throw your way that don't involve flaming singularities.