I got a new chair from ikea which came with armrests. I didn't want to screw them on the chair, because I generally don't like arm-rests on my chairs and they don't fit under my desk. Not mounting the arm-rests left some blank nuts which didn't look very pretty.

3D-printer to the rescue - I printed some caps to hide the nuts

local-guru.net/blog/2011/11/12/hiding-some-screws-on-my-Chair