The Digitech JamMan Express XT is a handy way to loop and do overdubs, layering loop on top of loop.
Silent Clear enables you to stop or remove a loop pattern, without having to turn your amp volume down as you do it. DigiTech thinks of everything and is one of the best brands for effects devices, although I love some of them a lot more than others.
It takes batteries or a power adapter, is cheaper than the Ditto, has 5 more minutes of looping memory (total of 10 minutes). It can be daisy chained to other Digitech JamMan loopers for multi-tracking and they synch, it has LED lights so you know where you are (Record, Play, Overdub), and it has stereo in/out.
For the price this is a fantastic looper, really easy to use with straight-forward controls and a simple interface. The Jamsync function is a really neat addition for people who like to create massive loop soundscapes. The Silent Clear is really useful, as i mainly use it for creating a backing track mid-song to solo over, and often need to change riffs later in the song. Only downfall is that it's maybe a little too simple, double tapping to switch the loop off can get tedious.