Apoptosis Gem - Which lines in your project need to die?

While this gem is kind of a joke, reminding you of older code that was written a long time ago when you knew less about the problem domain than you do now (since you've been working on it for the last year), checking older code for refactoring/rewriting opportunities can make life easier for you in the future or whoever maintains the code after you.

Speaking as someone who inherited a huge untested codebase - debugging those sections that were written early on and work most of the time, but have never been refactored to take advantage of things that were learned later on in the project, is pretty unpleasant.