If you like to tinker with motors you'll find that a lot of motors from toys and equipment have stubborn pinion gears stuck on the shafts. These can be a pain to remove, and while prying on them or punching them out with a hammer can sometimes work, you risk damaging the motor.
This will show you how to make a very effective gear puller with basic tools and next to no cost.
Step 1: Cutting the frame
I used a piece of 1" square steel tubing with 0.1" wall thickness. I cut it to a length of 0.75" with a hacksaw, it doesn't have to be pretty.
Step 2: Drill the screw hole
Since I'm using a #10-32 screw for my puller I drilled a 5/32 hole in the top wall and tapped threads into it.
Step 3: Cutting the shaft slot.
There are a variety of ways to do this. Hacksaw, dremel cutting disks, drilling more holes in a path...
Step 4: Modifying the screw
Center the hole the best you can on the end of the screw, a 1/16" is a good size to use as most motor shafts are not that small. You should drill at least a 1/4"-1/2" down.