When I first got my 360 and my brand spanking new xbox live connection, I figured I would try Halo 2 online('cause the system didn't have any good games on it at the time). The very first map I was in, there were people literally flying all across the map, and throwing swords. I thought that was a bit ridiculous, but I kept playing and did okay. The next map I wound up on was an indoor area, so I was sneaking around with a shotgun mostly getting assassinations. So everyone started accusing me of hacking because I was good at sneaking up on people.
That was both the first, and last time I ever played Halo 2 online.