I'd love to see either a
suction ball game (it's a shame I can't find any greater than two inches... but can you imagine having a target to aim at with these things?),
phlat ball (you thought Frisbees had a weird geometry?), or some kind of partnership with Nerf for some Nerf dart shooting game (would be great publicity for both parties).
And that's my reminiscence of childhood for a day.