ITT game coders, what do you use?

Myself:
FreeBasic with normal fbgfx for normal games and Perl with a truckload of CPAN stuff for "door games".

PyGame for prototyping.

C++ & WxWidgets for games with emphasis on getting lots of info to player rather than pretty graphics (e.g. military simulations). C++, SDL for 2D games.  Add Irrlicht for 3D games.  If it's just an FPS, a Sauerbraten mod is easier.

In case you haven't noticed, learn C++ (and the boost libraries).