Sonic Dust

Sonic Dust is a synthesizer that explores glisson synthesis.

Strum Machine

Strum Machine is MIDI guitar based step sequencer designed to add strum features to physically modeled and sample based string synthesizers that don't have their own.  It's useful for musicians who don't play guitar.
 

Microelectronic Bikini

Microelectronic Bikini is a hybrid synthesizer that explores FOF or "Fonction d'onde Formantique" Synthesis.
 

Spider

Spider is an experimental granular synth.

Eardrum

Eardrum is a synth-based drum machine with seven individual sound banks. Sounds wonderful but suffers from occasional CPU spikes.

Ploke

Ploke is a standard monophonic subtractive synthesizer built around a "styling" section which allows one to play with portamento, true glissandos, effective glissandos, or standard settings.  Waveform shape selections can be modified with a slider or lfo, pitch adjusted, slightly thickened up, and then destroyed in a a nasty "dirty" section finally to be adjusted overall by a hi, band, or low-pass filter.  The main purpose of this synth was to create something capable of producing automatic glissandos.

Twiddle

Twiddle is an experimental waveset synth with 128 waveset samples.

Gizmo

Gizmo is a triple gate and pitch sequencer with three sets of fm core based oscillators which can be run separately or merged into a low pass, band pass, and high pass filter.  Sounds are then passed into a diffused delay with individual pan and volume controls and is useful for creating rhythmic bleeps, blops, and bloops.

 Reaktor is a product by Native Instruments.