Simple indoor ball game
Cones / chairs / benches
4-corner dodgeball starts with 4 teams in their corners. When players are hit, they join the team that hit them. If one team is left with no players, the space opens up for another team.
Divide the room into 4 playing areas using cones (or whatever).
Create 4 even teams.
Whenever a player is hit, he joins the team who hit him (so players are constantly changing teams).
If one space has no players left in it, take the cones away to open up a bigger space for a different team.
Play until there's only 1 team left!