mistakeIt was just a silly mistake - no need to apologize.
errorHe admitted that he'd made an error.
slipIt was an understandable slip.
mix-upThere was a mix-up with the bags at the airport.
gaffeI made a real gaffe by calling her "Emma", which is the name of his previous girlfriend.
oversightThe payment was delayed because of an oversight in the accounting department.
slip of the tongueIt was a slip of the tongue - I meant to say "painless" not "painful".
misprintThe newspaper article was full of misprints.
typoRead over your CV carefully to make sure there are no typos.