Interview tip: Always have an iterative version ready !
Furiously writing down a 5 line recursive solution in 2 mins is a near certain invitation to rewrite it iteratively(" that's great, but what's the risk of recursion? Oh so you know about stack space overflow, well can you try it without recursion?").
And it's not always trivial to convert it on the spot without prior preparation.
Simplest example: post order traversal of binary tree.