The pen trick always worked really well for me with consoles (VB/GC/N64/. But for SNES/N64 games it never did the trick. They've got smaller screws and the holes they sit in are pretty shallow.
I know that for some of the really old NES games, though, a little flathead screwdriver will work. My Zelda and Hogans Alley have these screws. I was hoping my Mario Bros would, as it would mean perhaps it would contain the JPN->USA converter. (At USA launch I believe they didn't have the US game PCBs made yet, so they opted the half-assed approach).