Water guns, unless my husband is involved. He is brutal! But it’s so fun to arm the whole family with super soakers and go crazy. Someone always ends up going for the hose and we all laugh until we’re in pain.
Also, Nerf guns! We have family Nerf wars too. There’s a whole system where we randomly assign guns, divide into teams, battle (three hits and you’re out), then swap guns, and repeat. In bad weather we battle it out in the living room. In summer, one team makes a stand up in the wooden play set and the other team has to storm the play set and take over. All good fun unless you get hit in the face or neck. ouch