[DiGiTaL_AnGeL]

Well, I don't remember the name, but it's that mission where you had to get on a taking-off airplane with a bike, kill everyone aboard with a knife while dodging oncoming barrels, and then jumping off the plane.
I also liked the one where I had to fly behind a plane, then get aboard while jumping from my own plane, then again kill everyone aboard, but this time with a machine gun, Scarface mode.
...and the one where I got back to Liberty City, pretty good idea.