BZFlag is a 3D, multiplayer, tank battle zone, capture the flag game that pits players against each other in a networked environment. It runs on Windows 95/98/NT/2000, Linux, MacOS 10.x, Irix, Solaris, and others. An OpenGL accelerator is highly recommended, but it is playable with 3D in software.
Formido is one of those games where you are loaded with some guns and you go shooting different things. "Things" in this case are big, ugly, alien insects. The goal is to kill as many of these as possible. Eventually, they will overcome you, but you must struggle as long as you can. There are some power-ups to aid you in your quest.