The classic games use a regular Phillips screwdriver, but I found the perfect tool for the triangular screws used on the originals; I took a Torx T10 screwdriver and ground off every other ridge using a Dremel cutoff wheel.
You only need two (TA20 and TA23), but it never hurts to have extra security bits, never know when they'll come in handy.
Mattel used two different sizes of these, one the triangle is almost the exact size as the head of the screw (TA23), the other is obviously smaller (TA20). You can make one bit that will work in both, but one small enough for the small size can actually strip the head of the larger size if it happens to be stuck for some reason (rare in plastic, but you never know). The small size I think I've only seen in the earliest games (Missile Attack, Auto Race, etc), the TA23 size is the most common. Works in most of those disposable games/toys too, like the McDonald's Happy Meal games.
There's also an exact replacement screw you can get with a normal phillips head... I have a box of them at home (I can check the screw specs tonight), the head is the same size, and the threads are exactly the same, so you won't damage the hole putting them in. Handy if it's a game you think you will be opening a lot for some reason (or if you just hate those damn screws... )