Alarum.

I know what you're thinking: "Surely the android doesn't need yet another alarm clock app.", and normally I'd agree with you; but I wrote this app. because I couldn't find a simple non-fussy alarm clock which worked the way I wanted it to.
I get up at the same time most weekdays, except Mondays; but I don't need an alarm at weekends: Alarum lets me set each day independently, and once it's done, it's done. It's one less thing to have to remember.
Setting up the alarms is very quick and easy too, alarms on the hour are set with two screen touches, no fiddly scrolling required; and the paid version is pretty configurable too.
Generally, I set it to wake me up gently, starting quietly so that I have a chance to silence it before anyone else can be disturbed.
There are also "one-off" alarms; which I use all the time; for everything from reminding myself to check the stove, to making myself stop bothering the computer and go and do something less sedentary.

And now, the obligatory screenshots.

Apposite Software