A fantastically designed, well balanced game- still my favorite over all the other Mario Kart titles.
The three difficulty modes offer a decent challenge for everyone, and this is the Mario Kart of old where you only got the most powerful, yet cheap weapons when you were behind (Stars, Blue Spikeys, Red Shells, and Lightning bolts). If you were ahead you got a solid selection of offensive and defensive weapons that took skill to use effectively, such as the green shell that required aiming if you wanted to hit someone, or the bananas that can be strategically placed to slip up the competition and keep your place at the top secure. This made for well balanced game play rather the random free-for-all of the newer Mario Karts, none of which I have enjoyed as much.
All in all, if you're looking for a N64 game to fill up some time with your old school console, you can't go wrong with Mario Kart 64. Just make sure you get some extra controllers for your friends!