At work, there are several individuals who use "acrost" instead of "across".
On the boards, one of my pet peeves would be the use of "would of", "could of", "should of" , etc.,
rather than the correct "would have", "could have", "should have"
or the appropriate contractions, "would've", "could've", "should've".
It is both a noun and transitive verb.
Ya know, I been a meanin to tell you that I run acrost some old pics of your boat and I would of sent them to ya if I could of afforded a stamp and I know I should of but Im gettin lazy in my old age.