"Unreal Tournament 2004 is closed source, but it's one of the few
commercial games which also provide a native Linux port.
"I can say UT2004 has everything one would want from a shooter
game: it has many types of weapons with secondary fire mode
available, vehicles, several official modes of playing, like the
Onslaught mode which is pure fun in my opinion, and combines both
DM/TDM skills with vehicles, team synchronisation and, yes, brains.
Because being late at a power node, even with two seconds, can cost
your team the entire game or round. It's truly a game for
teamplaying, and you'll never suceed in a 8vs8 Onslaught game all
by yourself, no matter how good you are. You'll need to know how to
wait in vehicles for your teamplayers, and when. You'll need to
have each player with exact tasks, you'll need to know who your
best manta/goliath/hellbender players are and let them use it at
full potential. The Onslaught mode will be one of the best
experiences of the game in my opinion."