A friend told me a week or so ago that you could get out of an assassination by spamming the B button just as the person is going to assassinate you.
I tried for about the first 20 times and give up. Today I was playing FFA and a guy came behind me, I hit B once and it glitched and I did some kind of super beatdown and earned a showstopper medal.
If this is already common knowledge then I apologize, just throwing -blam!- out there. The video is under LOLStopper in my file share incase anyone is interested.