This Game should be done Inside.

4 rubber balls

Split into 4 teams.
Divide the play area into 4 quarters.
Each team stands in their quarter.
On 'GO', the balls are thrown at members of other teams.

When hit below the shoulders, a player joins the team that hit him.
At the end of 5 minutes, the team with the most players wins.

If two teams get eliminated, you can change the layout to halves instead of quarters.

With balls flying from all sides, it helps to have some judges to call the shots.