1. Go on tf2
2. Be a pyro
3 go to a sentry
4 keep using your secondary weapon (shotgun, or flaregun) taunt.
5 soon or later a spy will try to zap the sentry
6 you just got a kill and achievment if you didn't get it already.
7 watch as the spy calls you a hacker.
I did this before on ctf 2 fort, the spy was all like OMG HACKS it was so hilarious i was just doing this for fun.