Shooting yourself in the foot in various programming languages

The proliferation of modern programming languages (all of which seem to have stolen countless features from each other) sometimes makes it difficult to remember which language you're using. This guide is offered as a public service to help programmers in such dilemmas.

[Note: as the basic collection has grown steadily older and older, I have tried to update it with some languages (and some OSes, admittedly) with which I am at least passingly familiar. Any assistance in this matter is appreciated; please send me e-mail at tuckers (at) reed (dot) edu if you have anything to add. Thank you.]