Alright, this time I really give up on eliminating start up rattle.

[pothole]

Do you know what I think that noise is?

I think it's the starter motor sticking momentarily. Here's why.

My car makes exactly the same noise. When the ignition barrel went funny, causing the starter motor to stay engaged until you twisted the barrel back a bit, the noise carried on much longer - basically until you twisted the barrel back to disengage the starter.

I made a recording of it before I had worked out what was going on:

http://www.youtube.com/watch?v=QTy8jvx0VrY