Originally Posted by 2DLogic
Another way to tackle the task would be to do some digging and find out what your friend's next project will be and gear the purchases towards that specifically.
Yes, this. That's always excellent! Tailoring a present specifically to what the person is working on would be really awesome.
I'm always a big fan of craft foam, and you can get a 12 in x 8 in (estimated) sheet for maybe a dollar at Walmart. (Granted, you'll probably need $20 worth of foam to construct anything sizeable). This can be used for all sorts of accessories, details, or even be used as a base for armor itself. I'd love that, personally!
Clay or paint are also good options. Model Magic tends to be a hit with my friends, because it can be used for pieces that need to be light weight. Sealants are wonderful too-- for example, clear spray varnish or modge podge.
Best of luck shopping!