There is an attack that some people have dubbed "lag hacking", and its gaining popularity in multiplayer games. There are at-least two ways of creating artificial latency. One method of introducing artificial latency is using a lag switch, where the user intentionally disconnects their network cable. Another method is using a flood of syn or udp packets to cause controlled and predictable disruption in the game so that a player can gain an unfair advantage. Artificial latency attacks affect a large number of multiplayer games.
Some game companies have been made aware of this attack by their users, but are ignoring this vulnerability because they don't have a solution. The tools to carry out this attack are simple to construct, readily available and easy to use. They will often spoof the source IP address to make the attack difficult to trace.
So security.se, lets come up with a solution to this problem. But first lets talk a bit about game protocols. Online games commonly use UDP due to decreased latency and overhead, but this also increases the susceptibility to spoofing. Game protocols can use Latency Hiding to decrease the "perceived latency", but this may increase the impact of artificial lag. Multiplayer games often use a p2p architecture, for example Hydra: Peer-to-Peer architecture for games, and a peer is easy to flood. The Unreal network architecture is well documented, and is also vulnerable to this attack. (If there is another resource I should list, let me know!)