matt wrote:
What's the most flexible type of screw, ie one that won't break when
bent? Steel and brass doesn't seem that flexible.

I have an application that needs a screw that won't sheer if bent more
than 20 degrees (the application is a bit complex to go into here!).

A thought - are there screws made from thick wire (5mm or so), as is
the case with wire nails? That would be ideal as wire nails are nice
and flexible.

Thanks

You are on a hiding to nothing. All screws will eventually fatigue if
subjected to that sort of strain.