Create an "item_pballgun" entity, then press the + button to add a key, and add "type" "stingray" (or whatever you want to use -- see the link I posted previously for all the types -- they should also be in the entity help, click on the "?"). Flags are simply the "flag" entity. I'm not sure what you mean by "team wall." If you mean an invisible wall like in dodgeball, it's just a clip brush. If you mean a border that can't be crossed in siege mode (defense can't exit the base), it's just a base entity, but you have to set up your map for siege mode.