U-he Triple Cheese

Triple Cheese is a unique-sounding freeware synthesizer plugin. Triple Cheese doesn't use any of the classic synthesis techniques – substractive, FM or additive – but various forms of comb filter i.e. very short chromatically tuned delays. The three cheese modules in a row either generate their own signal, or process the output of the previous module.

http://www.u-he.com/cms/triple-cheese