Well, it depends!
Beer Spills
If someone is pushing past me in a pub on their way to the bar or to the toilet, that person may say to me as they bump into me, "excuse me" or "pardon me."
S/he, the bumper, is asking to be excused or pardoned for a minor infraction, namely endangering or even manifesting a beer spill.
While it is technically a question (will you excuse/pardon me?), it is typically offered more as a declarative statement in which the bumper expects me to excuse or pardon him or her.
In fact, I might even be considered rather rude if I did not excuse or pardon someone who made me spill my beer, especially after s/he asked to be excused/pardoned.
Sometimes, if I'm minding my own business drinking a beer, and someone bumps into me without saying anything and spills my beer, I might get irritated enough to bump back by saying "excuse me?" or "pardon me?" In this context, my words are offered as a gentle, ironic rebuff. The double irony is that my words mark some disinclination to excuse or pardon the bumper.
In this beer-spilling sense, excusing and pardoning and even forgiving someone are synonymous. To excuse or pardon someone who causes a beer spill is little more than a politesse. And a rebuke by the bumpee with an "excuse me?" or "pardon me?" is a reminder to the perhaps thoughtless bumper of the need for this politesse.
Big Spills
But how about the situations in life where the bump is something rather more substantial than a beer spill? Maybe an oil spill with economic, financial and ecological consequences. Or a physical assault perhaps resulting in a literal blood spill. Or maybe something more emotional as in a metaphorical breaking of the heart and copious tears are spilled.
