I built a MAME arcade game that was capable of playing 1000's of arcade games. I started an OOT thread about it a few months ago
here. Its been a hit at parties. Total cost was approx $1,600, though you could build it for less. When I started I had no woodworking skills and probably moderate computer and wiring skills, so even if you dont have any skills yourself, they are not that hard to develop.
I also vote for cornhole, washers or redneck golf for outside activities.