We were putting up some shelving in a closet and inadvertently drilled a 1/4" hole through the drain pipe from the washer upstairs. Can we just plug this hole with epoxy of some kind or do we need to replace the pipe?

The problem with using epoxy or similar materials is that it often leaves a ridge or bump inside the pipe, which can become a clog point if something catches on it when going down the drain -- However, if it's only a clothes washer drain, then the likelihood of something hanging up on it is very remote.

I'm kind of anal retentive about things (a loquacious way of saying I'll do whatever it takes to avoid being sued), so I'd likely cut it off square right at the puncture and then rejoin the pipe with a Mission, Fernco or Pro-Flex shielded coupling.