I've got about a jillion security bits, but none are triangular.

I can usually unscrew the triangles by using two jeweler's screwdrivers- 1 that's just shorter than the edge of the triangle, and another smaller one in the middle to keep the first one in place. But I've run across a few screws that I couldn't get out that way.

I'm ashamed to say that I have used a Dremel cutoff wheel to cut slots on screws so I can use a flat-blade (cutting partially through the case, if need be).

Somehow, I've wound up with half-a-dozen of those Torx T10s, so no big loss. I used the ground-down one on Auto Race and Football 2 and it worked well on those two, but I'm sure the actual bits are best.

Speaking of opening games, I've been surprised at how many repaired games I've gotten off ebay. A few times it's been battery damaged traces that were repaired with wire jumpers, and there have been several that had broken plastic support pieces that were fixed to various degrees. Then again, I got a Mattel Basketball where the 9v battery clip had been pulled off and the wires were just twisted together- red to black and black to red! That game has 3 bare dies on the PCB, and one of them had melted all of its bond wires. But the ROM bits are still visible!