I have been going through cases like mad trying to find one that fits me best, and so far I've just been changing them up everyday. My current favorite is the Incipio Feather Ultralight Hard Shell Case (that's a mouthful!). While is has a minimal design, it offers up great protection for those that aren't ready to use a bulkier case on the Z10. It has a simple snap-on design and fits around the sides and back of your device to keep it safe from small drops that would otherwise result in big damage.
I've always liked to go the minimal route with my cases. I don't care for the added bulk of a larger (yet safer) case most days, but I still realize that drops do happen so something is better than nothing. For that, the Incipio Feather Ultralight Hard Shell Case does a great job. It doesn't add very much bulk to the Z10 at all and still has a great feel to it.
The case snaps on quickly and has openings for all of the ports and buttons on the BlackBerry Z10. The top and bottom of the device are left open a bit but the case does cover up the corners and the back nicely. There is no "thumb gouging" (where a case digs into your thumbs while typing) which is a plus for me on this one.
I did have a bit of trouble getting it to come up around the edges of my Z10 at first, but a firm press on the back of the case gets everything where it needs to be and it holds on tight.
I was also a bit worried at first that this case wouldn't keep my Z10 safe from accidently drops, but the design covers just enough of the corners to keep the pavement-induced divots out of mind. The Incipio Feather Ultralight Hard Shell Case is also available in a variety of color and since it's easy enough to get on and off, you can change it up to your liking as you see fit.