... has an "else" whether it's written or not. Choose carefully whether to skip writing it, but always know it's there

I try to impress that not as much upon developers, but religiously upon folks writing requirements. Many pieces of code work just fine without the else, but the amount of bugs and rewrites due to someone either not considering "but of course it always succeeds!" or because there was an implied else scenario in their head that they just didn't bother to write down are almost innumerable.