Gamer's Proxy
Proxy for games that emulates network conditions like ping and lag.
...This program allows gamers to fake their ping and packet loss. Only games which allow direct IP connections are supported - this program will not emulate the game server and will not advertise itself on any master server of any game.
The idea is this:
game client -> proxy -> game server
Demonstration video:
http://youtu.be/2VWNhmfD1Qk