Detective Comics ('37) #826 by Paul Dini is a personal favorite. #0 and #703 of the same series (both by Chuck Dixon) are also very good for gimmicky event tie-ins.
Batman ('40) #251 by Denny O’Neil is another classic.
Shifting away from Batman a little (but not too much), Nightwing ('96) #51 (also by Dixon) and Birds of Prey ('99) #8 (Dixon strikes again - what can I say, the guy does a good oneshot) also come to mind.
Outside the Bat-Family, Wonder Woman ('87) #20 is excellent. There are probably other good non-Bat-ones that I’ve read but I’m drawing a blank at the moment. I’ll edit as I think of things.