I once saw an acoustic guitar player perform alone, yet somehow he was creating some synth-like organ sounds as he was playing. The pedal he used was the EHX freeze. Since I am always happy to steal other people's tricks, I ordered one to see what I could do with it. I ended up doing mostly the same thing as the other guy, but it is a fun trick to have.
Build quility is as solid as EHX always is, strong metal casing, the thing could probably take some serious abuse.
The freeze takes a tiny bit of your guitar signal and sustains that as long as you want. You get to select if you want it to sustain as long as you step on the pedal or to have it latch on until you step on it again. Using it, you get to create synthlike sounds, almost sitar like at times. Really adds a some layers and depth to your sound while strumming chords. Of course, you can also use it to endlessly sustain that one note at the end of a guitar solo, or let one chord ring out while you noodle lead parts over it, but I like it best for adding that layer to strumming chords.
Controling it is a bit tricky, I must say. If you step on it too early while hitting the chord, it can just sustain the sound of your pick or fingers hitting the strings in stead of the sound of the ringing strings. Not very pleasant to listen too. Hit it too late, and it doesnt pick up enough sound to really ring out. I use it in songs where I also sing, and it gets quite challenging at times to get the timing right. With some practice though, it is a very useful tool to have on your board, and also a rather unique one. It is not one of the commonly used effects, but certainly worth giving it a go.