SE64 is a monosynth that makes retro computer game noises.
It has two oscilators - one can be set to saw, triangle, sine or a variety of PWM waveforms. The other oscillator is a triangle wave which is ring modulated with oscillator 1. There are EGs for pitch, pulse width, amplitude and filter cutoff. One important feature is a very fast arpeggiator which can recreate the "chord" parts from C64 SID tunes. There are also two bit-crusher effects.