Even a jazzy real-time voice communication system can't make a good game without a solid set of gameplay features behind it. Fireteam comes with four different types of games:
BaseTag: In this scenario, the goal is to destroy the other team's base, while keeping the enemies out of yours. Unfortunately, most Basetag games end up being who can kill each other's base the fastest, since most newcomers are apt to go on the offense rather than defense.
Capture The Flag: Pretty self-explanatory, though it's not the CTF-style game we (Quake players) are used to. Instead of one flag in each base, there are multiple flags scattered across the map. Your goal, as a team, is to capture as many flags as you can (by walking over them), while holding off the enemy from capturing more. The longer you hold a flag, the more points you get. Unfortunately, since there are so many flags scattered across the map, it becomes not so much an "attack, hold, defend" type game, but rather a "wait for enemy to leave flag, use scout to steal flag" type game.
GunBall: Similar to the game "Powerball" from the show American Gladiators, each team tries to muscle the ball into the other team's goal. An interesting addition is the use of weapons to cause fumbles and other such things.
Deathmatch: A no holds barred frag fest, with a cool twist. The first half of the match is spent racking up as many kills as you can, and for each kill you receive a "life-point." In the second half, it's once again a huge blast-fest, but this time, you can only respawn as many times as you have life-points that you earned during the first half. The team which still has players standing at the end of the game is the winner.