The Night Stand clock app, orginally made for iPhone, has a lovely version for iPad. It has several interfaces to choose from which I like, and I finally got the big clear clock I wanted in my living room. :-)
The different faces are just beautiful. Amazing design.
It's an alarm clock too, although this seems to be less polished than the visual interface.
Also, in my occasional efforts to "exercise" the 'pad's battery by running it flat so it does not die, the iPad has been running the clock, screen on, unplugged, for 12 hours now, and there's still 30% battery left! (Of course this does not tax the processor much, and that's an influence. Still.)
Update: it ran for over sixteen hours all told!