yes yes yes, more options than a man should be allowed.
Car window motors - excellent, the power source might be a little tricky but then again maybe not, anyone know about the gearing on one? because if they spin as fast as a power window opens/closes that would be an ideal speed.
bench grinder - easy power source, gearing might be an issue and I'm trying yo remember if grinder motors lock, I think I remember being able to freely spin my dad's bench grinder as a kid.
Actuator for a truck tonneau cover - looked quite spendy from what I gathered, but would make a very smooth coin door lift, but I think the cheapest one I found was around $250,
I really appreciate all these great ideas, I'm thinking with all the brain power on this forum arcade builders could someday rule the world...currency would be reduced to quarters only, and wars would be settled by high scores.