Its not a video idea, but I've always wanted some kind of deathmatch game where all of the weapons were inflation/weight gain based. There could be a dig-dug style pump gun that shoots a hose into your enemy and you blow them up till they pop, or a weight gain ray gun that adds mass to its target until bursting. I have plenty more ideas for weapons but the general goal would be to pop your enemy.. The health system would work as a bar that fills up as your character expands, but eventually goes down if you don't take damage for a couple seconds. Power ups like elastic skin for extra health and anti-gas pills to deflate yourself quicker could also be added to change the gameplay up.