How to make a command block take away certain items in your inventory in minecraft?

I'm making a server, i need to be able to make it so in some minigames(like hungergames), it clears all of the items you got in hunger games from your inventory. OR If its more specific like i'm giving someone a bow and some arrows for a game and i need to be able to take them back after, what is the command block command for this? If there isn't one is there a mod?

Just get plugins, bukkit.org.

/clear but making a minigame with only commandblocks and redstone is very very hard, I recremend you get some bukkit plugins