The function of the appendix, and possibly "junk" DNA
I read recently that the purpose of the appendix is to repopulate the digestive system with the appropriate mix of micro-organisms after a severe bout of diarrhea. People without an appendix apparently have a much longer, more difficult recovery.
As for the "junk" DNA, I've read that more and more of it has a purpose. Apparently it can affect the timing of the expression of some genes, and some of it assists replication.
I think the natural human tendency to disparage what we don't understand is operating here more than evolution dragging around a bunch of garbage.
Arf