Terrarian 2
Plantera
Or the rocket launcher, or the proximity mine launcher, or if you are good enough the grenade launcher. People use those weapons??? they harm the user, they are terrible!!!
Once again, blast radius. Also the first two also apply to the infinite ammo already in place. This only effects the guns you mentioned (that are awful) and the snowman cannon. Anything else has a fixed blast radius or uses special ammo.