Danelectro SKJ-1 Spring King Junior

This pedal does what it says: it's a reverb pedal with springs in it. Nothing more, nothing less. It's easy to use and sounds fantastic.
For me, it seems to work better before the amp rather than in the effects loop.

The reason for the 4 stars for quality is that the DC input is at the worst possible place, the paint is quite fragile and the edge of the footswitch is ground in a weird way.