This is one of the workhorses of effective communication in Mexico City. A huevo (ah-WEH-bo, lit. at egg) is used in two ways. When used as an adverb it means a fortiori. Now, for those of you who do not know latin, that means "for a still stronger, more certain reason". That means if you do something a huevo, you're forced to do it. When used as an interjection, ¡a huevo! means "fucking-A!", "you bet!" or "I told you so!"
Both uses are informal. However, there are some ways around its inappropriateness. For instance, instead of a huevo you can say a Hüelfo, como dijo el alemán, which means "to Hüelfo (not a real place), as the German said" or a Wilbur, which means "to Wilbur". The educated ear would get the message right away and nobody would be deeply offended.
Pancho: ¿No te caga hacer las cosas a huevo? (Don't you hate doing stuff because you're forced to?)
Poncho: ¡A huevo! (You bet!)