I like Tensor quite a bit. It’s really versatile – pitch shifter, time stretcher, virtual tape loop, reverser, random glitcher, etc.
It’s got some really clever features. The two switches can be momentary or latching. It’s listening even when “off” (if powered), so you can immediately slam your audio into reverse for instance. If you’re using it to slow down time “live”, instead of the buffer running out, it resets at what it guesses is a musically viable time.
It’s not perfect in its pitch or time shifting (it’s based on a Spin FV-1, not an FPGA or something), and you can take advantage of that to impart some interesting character.
And then there’s the hold modes, ranging from relatively basic looper (with or without overdubbing) to a double-buffered mode that is hard to predict, but sometimes is almost like a normal delay and sometimes more like someone is playing counterpoint with you 
