Paintball is a game played by the main characters. The sport makes occasional appearances on the show, in one episode Howard and Leslie Winkle participated in sexual activity twice in the shed. In the same episode, Penny accidentally shoots Sheldon's Seat on the couch with a gun, and when they decide to invite Penny along, Sheldon takes revenge by shooting her, leading to an argument.
Sheldon then sacrificed himself for his team. The gang went celebrating their victory and then Sheldon pointed out that he promoted himself to the rank of major before he was "killed."
- Paintball on Wikipedia