I really like Perforce as a source control system. It is clean, and solid, and has great support. But its merge tool blows giant chunks. It looks like a Win16 application, and uses an entire spectrum of confusing (and ugly) colors. I could deal with any of that, here's the clincher: it occasionally inserts newlines into the merged files! Identifiers get split across two lines, and the compile breaks. What's up with that!?