Without further gubbins from me here are the designs:
A rather neat machine due to Prof. R.P. Feynman
(In response to comments I should add that Prof Feynman designed this machine to make a point about the impossibility of perpetual motion rather than to attempt to build a perpetual motion machine).
An underwater spinning donut
A hi-tech perpetual motion machine
A rather clever piston based machine
Important disclaimer: Naturally, being of sound mind, I have never attempted to build any of these devices. The consequences should you construct a working perpetual motion machine will certainly be dire - including, no doubt, the now proverbial "being torn apart by a rampaging mob of respectable physicists". I accept no liability in the case of such an event.