Proprietary Screw Drives
This page details the various uncommon screw types that can be found in some consoles. Most consoles use standard Phillips-head screws, but some, especially Nintendo consoles, use screws that aren't necessarily proprietary but are nearly impossible to find in conventional brick-and-mortar hardware stores. Luckily, many of the necessary screwdrivers can be found for next to nothing on eBay.
The 4.5mm gamebit was used not only by Nintendo but Sega as well. It was found in: