From CraftMinx's 365: A Granny Square A Day, originally from Leisure Arts 99 Granny Squares
It doesn't even have a pretty name, but apparently it's #82 from Leisure Arts 99 Granny Squares.
I'm going to call it Spiky Granny.
I didn't have a pattern to go on, and I'm not terribly practised at spike stitches, so the sides of the square have been brought in a little, making the corner's appear a bit too prominent. However it's just your basic granny square, with some spike stitches in the sides. I really really like it! It's a nice plan granny, with a twist!