Heroes is similar to the "Tron" and "Nibbles" games of yore, but includes many graphical improvements and new game features including 12 original soundtracks, 94 levels (in 10 different tilesets), and five gaming modes including Quest (the classical Nibbles), or Kill'em all (squish the lemmings).
XPilot is a graphical multi-player maneuvering game with less-exciting graphics, but more speed, tactics, and insults. Some people also use it for UDP network analysis. Over the past eight years of playing and development, tons of features have been added to the game, from basic weapons like shotguns and missiles to more recent ones like phasing devices, invisibility, or hyperjump.
Njam is a full-featured cross-platform Pacman-like game that uses the SDL library. It features single and multiplayer modes (local or network), duel games where players compete against each other to get more points, cooperative games where players cooperate to finish as many levels as they can, and great music and sound effects. It includes customizable level skin, many different levels, and an integrated level editor.