Colin McRae Rally 2.0 is a visually and technically impressive GBA game especially when it comes to the Single-Pak multi-boot 4 player link mode. Using 3D models and realistic physics, this is a more simulation-style racing title as opposed to more acadey (never use the break) racing game.
Up to four players can compete from one game pak, there are multiple vehicles and tracks available, and it all plays with a smooth frame rate. Definitely one of the cooler GBA Single-Pak titles I have covered so far.
This is Single-Pak link!