What are some extremely cool looking Rocks/Minerals that are not commonly found in a collection

My girlfriend's Birthday is coming up and she is very into geology and I know a whole lot of nothing about it. I have looked around online at some different ones and found the rare ones that cost an arm and a leg. But I want something that will put her in shock when she sees it. Can I have a few names of some very just colorful and awesome looking rocks/minerals that are very unique and not in a regular collection? Anything is appreciated at this point and GREAT thanks for the time that anyone puts in to help me with this dilemma.