XPressor

This is by far the most musical saturator I have come across so far. The combination of saturation and light compression results in an abundance of smooth harmonic overtones that enhance pretty much anything you slap it on. My favourite is using it on any kind of bells (synth or sampled) in wavefolder mode, it really makes the resonances sing and the high end shine in just the right way. And it consumes less CPU than most others, even with 8x oversampling enabled. The fact that this is available for free is simply amazing, anyone using it should really consider donating a few bucks to the developers, the deserve it.