When using a Mac OS X computer, it's easy to forget that it's just Unix running under the hood ... until your iMac graphics card dies and all you can do is use single-user mode, which has no GUI ... then you're reminded very quickly that it's all just Unix.
Take emptying the trash, for instance. Graphically, you right-click the Trash Can icon, then select the Empty menu option. From the Mac command line (Terminal) you just do this:
rm -rf ~/.Trash/*
It's funny how simple that is from the command line.