"Ни фига себе"="Ни фига се" I don't know why it is written нЕ фига instead of нИ фига.. This is very popular informal phrase (for teenagers especially) and means sense of wonder. We use often too: Ни фига себе = нигада себе = офигеть = ни хера себе = ни х*я себе = ох*еть = в натуре? = да ладно? I guess in English it is something between = that's how it is! and Holy shit

Cool! I've want to break my arm too!

Thanks everyone :)

I love your questions!

Не фига се - very informal =) only for friends