La vache!

(une) vache ("vah - sh") = a cow

The word becomes interesting when one looks at its alternate meanings:
1/ It is slang for mean, nasty:
t'es vache! = you're mean!
il m'a fait un coup vache = he pulled a dirty trick on me

2/ "vache de" is a locution that translates to "hell of". E.g.
il m'a offert un vache de bouquin = he offered me a hell of a good book

3/ As in "bastards":
les vaches, ils ne m'ont pas attendu! = the bastards didn't wait for me!

4/ la vache! indicates surprise (God!), admiration (Wow!), anger (Shit!)...