I'm wondering about situations where the gender of a noun changes its meaning or sense. Spanish has a few words that can take either gender in their article. The only one that comes to mind is mar, the word for "sea," which is usually a masculine noun but is sometimes considered a feminine noun when used in more literary language, and in some idiomatic expressions.

A twist on this is adjectives that only take one gender's ending - an example being the Italian word figo which means "cool," as in "way cool pocket OED, dude" but is only ever given the masculine ending - ending it in an "a" changes it to a noun, and an obscene anatomical reference at that.

Are there cases like this in other languages, where switching the gender can greatly change the meaning?