Case
I actually have an Otterbox as well for my X with extended battery, and it works but I'm not a fan. I got it because my friends with iphones have one, and while it is very sturdy and I feel like I could throw it against a wall, I also feel its too bulky for my pocket. The outer liner doesn't feel as long lasting as I would like, it keeps feeling like its going to stretch and come off too easily.
I bought a Seidio Innocase Active and I love this thing much better. Still has silicon liner and plastic shell, but reversed order so the hard shell is on the outside. It feels sturdier for long life, and its smoother so it goes into and out of my pocket more easily.
It is a really tight case, so it takes a minute to put it on and I don't have any plans of taking it off anytime soon, but if I did it would probably be a pain.
Also, it comes in colors. Which is cool.