Yup, accents can be pretty critical. In Finnish, näin means "I saw", but nain means "I had sex with". This put a bit of a twist on a friend trying to tell me "I saw the rapist in the park!" when the umlaut dropped off...
You can differentiate the cases by the conjugation of the object though. "nain Annan" (genetive, "all of") is marrying Anna, while "nain Annaa" (partitive, "part of") is fucking Anna. But yes, learners of Finnish should definitely be careful with that verb ;)
I've always thought it awfully pragmatic that the Finnish word for "getting married" is literally "to go and fuck together".