Step one:

Create a new layer-set called SpikeGrenades.

First we have to construct the spikes, using the pen tool, draw the shape below in a new layer. Fill path #636363.

Add a Gradient Overlay layer-styles.

Step two:

Again with the pen tool, draw the small #959595 shape you see below.

Add a Gradient Overlay layer-styles.

Step three:

Duplicate the piece twice and position it going down wards, see picture guide for visuals.