Mad world was pretty damn good. I still rememeber seeing it on TV and the tingles i got.

I just watched them all again and the Mad World one still gets to me. I remember sitting in a movie theater seeing that on the big screen and thinking to my self fuck I gotta go get a 360. Though Gears 3 one is really cool too and has me fired up already, thanks Cliffy now I gotta wait a year.

I picked Mad World but I really, REALLY like the How It Ends trailer too.
Heron Blue is good, but I didn't find it as good as the first two.
 
I think that Mad World trailer may have sold more consoles than any other single piece of marketing this generation.

I vaguely remember pooping myself when I first saw the Mad World trailer.

I loved the red blood trailer, with the chainsaw dual

This is more the trailer I associate with Gears 2, and it might still be my favorite.