Whats your budget per gift? if you are sending loads out to past clients and important present clients its going to be difficult to get the right mix - when you know what you wants to spend post and i will post some ideas that we have done for people in the past.
I would say try to avoid the obvious though - keyrings, mousemats etc - i don't think people really use them (just my thoughts)
Printed desk pads work EVERYTIME - seems to be one that people come back to us for time and time again, i have even seen customer with their competitors names on THIER desks because the desk pads was so good.