Include a workbench so you've got plenty of room to work and keep your benchtop tools. Lining the walls with plywood means you can hang stuff just about anywhere, giving you a greater range of storage options. You can also personalise it with man cave decorating.
Maximise the storage power of your garage with a few sets of steel shelving racks. Store heavy and bulky items down low so there's no hard lifting and keep alie-items together with plastic storage crates.
A comfy couch and a wide-screen TV are a man's must-haves! Fancy adding something else? Just adjust the size of the walls to increase the ratio of relaxation.