A granular synthesis H9 Special algorithm. It was mentioned once early on in this thread, but it's worth repeating (no pun intended). I think that Eventide could raise the bar here with the extensive MIDI control and stereo configurations common to all their algorithms. I can think of only one competing product in a stompbox-type format.
The UltraTap algo comes SO close in many respects; especially with multiple parameters assigned to expression pedal / Hotswitch control. Fold in some aspects of PitchFactor algorithms [Crystals; H910/H949; HarPeggiator]. I'm currently using an 8 Step Program to sequence expression input to a PitchFactor and H9, for very controllable glitch / stutter / grain-like effects.
About all that's missing are the options for grain playback sequences, duration, more density control, …
