The EHX Stereo Memory Man with Hazarai (referred to as the SMMH round these parts) gets my vote. It has two really indespensable controls that arent found on most delay pedals. The decay knob adds reverb and the filter knob allows you to filter bass or treble out of the repeats. Being able to dial in a smidge of reverb whilst also filtering out the lows from the repeats results in a great ambient sound without a muddy low end.
It can also make repeats fade in rather than out which sounds really eerie, and another mode where holding the footswitch plays up to the last six seconds backwards. Plus reverse delay, presets, tap tempo and a looper!