...hm... as cool as master chief is, I would have to say samus.
sure M. Chief COULD use a sniper rifle and mines at a 2 kilometer range, but if they get thrown into an arena then technologically speaking, this would be like comparing wolverine and hulk. no mater how cool wolverine is, he wouldn't be able to do much against hulk.
BUT, going completely off topic now, I would like to see THIS fight: Bruce willis vs Chuck norris! THERE you definitively got a "clash of the titans".
...say if we use a time machine so they would both be the same age... ...how old is chuck now anyway?