1. Open a 500x500 transparent document, select the Elliptical marquee tool and make the base of the poke ball by holding SHIFT and dragging on the image. Fill the circle in with a nice bright red, I chose E20707 for the top piece of the poke ball
2. Create a new layer and select the Magic wand tool by pressing "W" on your keyboard. Select "Layer 1" and then click once with the Magic Wand on the red circle to get a selection out of it, once that's done choose a light gray for the bottom piece of the poke ball. I chose F2F2F2 for the light gray. Now select "Layer 2" and fill the selected area with the light gray you have chosen.
3. So basically you have two layers, a red and a gray circle that's overlapping the red circle. Erase the top half of the gray/white circle. Now CTRL + CLICK on Layer2 and Layer1 to get the outline of the circle. With the brush tool, create a BLACK rectangle going from the left side to the right side.
4. Select the Elliptical marquee tool again and make a BLACK circle in the center of the poke ball. Then add another circle in the circle you just created and color it WHITE.
5. Select the Gradient Tool and then pick the Radial Gradient from the top tool box. Set your primary color to WHITE and CTRL + CLICK on "Layer 1" and just add a simple gradient effect on the top piece.
6. Merge the two layers together and go to Filter -> Render -> Lens Flare and choose these settings.
Now go to Filter -> Render -> Lens Flare to add some detailing by using the settings below.
7. Once those two renders are applied, it should look like this.