In Balder2D, players control small probes which shoot tiny projectiles with which they try to destroy each other. It features a 2D overhead view of the playing field. Probes may be human or computer controlled.

This package provides a client interface to the X Window System, otherwise known as 'Xlib'. It provides a complete API for the basic functions of the window system.

GraphMonkey is a GTK#-based graphic calculator. It uses a simple interface to draw curves.

A free cross-platform library of fast C++ routines for plotting data in up to 3 dimensions. It can export plots to bitmaps and vector EPS, SVG, IDTF files. There are simple window interfaces based on GLUT, FLTK and/or Qt. MathGL can also be used in the console. There are interfaces to a set of languages, such as, C, Fortran, Pascal, Forth, Python, Octave.

A monophonic synth plugin that sends the sound from two sine oscillators through two sine waveshapers in series. You can control the vibrato, tremolo, portamento, the tuning of both oscillators, the oscillator mix, and the shape amount (total and split over both shapers). There is also an ADSR envelope generator that can control the total shape amount and the amplification (with controllable sensitivity for both), an LFO for the total shape amount, and a feedback delay. The shape amount and amplification is velocity sensitive, and the "Mod Wheel" MIDI controller is bound to the total shape amount.

These packages are either mandated by the core LaTeX team, or very widely used and strongly recommended in practice.