This isn't free stuff - this is because Linn lost stuff due to a stupid bug which the damned developers can't or won't fix.
Something cool to do with pistons: build a transformer.
A sculpture that looks like a car, then you flick a switch and it turns into a robot.
Probably very tricky to do without rotations, and no doubt a pain in the arse to power pistols (especially to make it go in reverse), but still it would be exceedingly cool if you pulled it off. :)