The NI-SPEKTRAL DELAY differs from the many other audio effects in that it uses real-time FFT (Fast Fourier Transformation) to split each channel of a stereo signal into as many as 160 separately modifiable frequency bands (even up to 1024 bands internally). The level, delay time and feedback amount for each of this bands can be set separately. Additionally, various modulation effects can be applied to the signal in the frequency domain, which allows for even further sound manipulation.
http://www.kvraudio.com/product/ni_spektral_delay_by_native_instruments_niToss out your old, boring stomp box delay and step into Spectron's spectral delay. Manipulate delay time and feedback based on frequency, add envelopes and LFO's, then tweak the left and right sides separately. Yes, it's that cool.
http://www.izotope.com/products/audio/spectron/delay.html