The BOSS RC-1 is by for the most user friendly and simple loop station out there. Featuring record, overdub and an undo / redo function. One of the handiest features however is the Loop indicator. It acts as a loop timer after you have played your initial loop so when you start over dubbing you can get an indication of how far through the loop you are. It is surprisingly very helpful.
The Boss RC-1 can be used for mono or stereo instruments and runs on 9volt Battery or AC power. The RC-1 can also be used with an external foot switch.