I recommend the Electro Harmonix 2880 looper. Unlike any other looper on the market, each button on the unit has only a single function and there are individual physical sliders for tempo, track volume and rotary pots (not encoders!) for input level and track pan. It can be operated without requiring visual feedback.
I agree. All is one button / one function on this looper. And no screen, no menu / submenu, nothing to read... very intuitive. Designed for performance in live. The new EHX 45000 is much better, with 100 loops x 4 mono tracks + 1 stereo. And the midi implementation on this 2880 / 45000 loopers have no equivalent : ALL the button / faders / function of the looper can be available by midi (and many more), so you can use every midi controller if you need (foot controller, table controller...) - really a wonderfull machine, despite the "oldies" look, and the fact most looper users don't really know the power of this looper.