In the spirit of "what's your favorite" threads, let me ask: What's your favorite programming tool?
Some tools that I've only recently discovered that I'm amazed I lived without (and their portage names):
boost libraries (boost) - Lots of extremely useful C++ libs. A huge pain to install without portage, but 'emerge boost' is cake
valgrind (valgrind) - Find memory bugs (segfaults/leaks/etc) without recompiling
kcachegrind (kcachegrind) - Amazing visual profiling tool


