Thanks for the links guys.

I don't especially like the invertible hammer design. I want something to pierce not pound.
And as for the pneumatics, I think a Magmotor or something as heavy and robust, at a ratio of maybe 4:1 (1:4? Which way round does it go?! ) would do fine... For a first bot atleast.

I've just realised, what I'd be making is a flattened mini X-Terminator with it's axe installed.

Keep the suggestions coming, don't hold back becuase osmething might be expensive.

And why can't I edit the topic title?!