Matched sets of raw materials and endmills suitable for milling them? You'd then use the raw materials to make them some suitable gift for next year....
Wrote this up when a wife asked what to get her husband on reddit: http://www.reddit.com/r/CNC/comments/2n ... uy/cmdgzrj
Any idea of what sort of projects he's planning on making?
One of the classic problems of the person who has just finished making a CNC machine is --- what material will I cut and test? (Please don't tell my wife where her plastic cutting board went --- I don't think she noticed the substitution) and the second is --- what will I make?
So if he knows what he wants to make as a "real" project, then you could purchase the material needed for a really nice version (assuming he's lucky enough to already have inspection tools --- while I agree w/ CNCgeek that a nice Mitutoyo or Starrett caliper or micrometer would be nice, if he's planning on working in wood or plastic (seems likely given the machine size) they're way overkill (that said, I have a nice Mitutoyo of my father which I keep in a case w/ my machine: http://www.shapeoko.com/projects/images/thumb_70.jpg
along w/ a Brown & Sharpe micrometer) and he may be planning on making do w/ an inexpensive digital plastic one (which frankly is easier to use, and quite as nice for woodworking and non-dimension-critical work so long as one buys a good quality unit w/ good battery life).
Just by way of an overview, you might find the Shapeoko wiki or interest. We have an FAQ: http://www.shapeoko.com/wiki/index.php/FAQ
and you may find yourself on the receiving end of some of the "Rules": http://www.shapeoko.com/wiki/index.php/ ... f_ShapeOko
(please don't buy him a 1,000 M5 washers though --- too prosaic for a gift)
An oft-recommended book is The CNC Cookbook: An Introduction to the Creation and Operation of Computer Controlled Mills, Router Tables, Lathes, and More by E. Hess.
If he's going to be doing woodworking, then he might be able to make use of finishing / trimming tools --- Lee Valley is a great source for those (and they have an excellent example of a "useful enough" caliper for quick, (non-critical) measurements: http://www.leevalley.com/US/wood/page.a ... at=51&ap=1
--- by way of comparison here's an entry-level made in the U.S. Starrett: http://www.leevalley.com/US/wood/page.a ... 3513,43546
If he doesn't have a nice block plane: http://www.leevalley.com/US/wood/page.a ... 1189,46791
If he likes miniatures: http://www.leevalley.com/US/gifts/page. ... 3212,70138
(they have an entire line of miniature tools, so you'd be set for gift-giving for years if you go this route).