Socks. They never fit me properly, as I have very small feet, and no matter how much I spend on them, I wear through them quite quickly anyway. I used to get my day to day socks at Old Navy, but theirs seem to have been largely discontinued, at least in Canada. I'm now getting them at Winners, and have finally determined that Calvin Klein fit best, and are decent quality, lasting about as long as any others (longer than the Old Navy ones did) and they're more formal than Old Navy's. I can normally get the CK socks at Winners for $12 or $15 for a package of three pairs.
Boxer shorts - I cannot fathom why a pair of boxer shorts, made of cotton, in general, costs more than $15, maybe $25 for high quality, lasting ones. It might be one thing if they were really comfortable, but only a select few fit really well, and those tend to be the expensive ones like Joe Boxer and Nautica. I buy whatever Winners has, that looks like about the right shape, and they are normally $10/pair or less, and that way, if it's not a good fit, I'm not out too much. Bluenotes (again a Canadian only store; sorry everyone else) used to have great ones, that would routinely be on sale for $15 per pair, or 3 for $12. I am not exaggerating. But, they changed their cut, and they now are definitely cut for teenage boys.
I also buy my athletic type (underarmour and its multitude of variants) boxers at Winners, around the same price. Reebok makes some great ones, and I'm also fond of Layer 8, and a new one I've just tried, called (I think) Degree 32. Very supportive, which is critically important for all of the moving and jumping I do on the ice all day.