Kajaani Kombat is a funny multiplayer game... and much more!
It is a rampart-like game (old arcade classic) set in space.

Kajaani Kombat is playable with two to four players, over the internet
or alternatively two players sharing one computer. It is also possible
to play over the internet with, for example, 4 players of which two are
sharing the same computer. Enjoy it with your friends!

WWW: http://kombat.kajaani.net/