we use several types of screw for 'user side' stuff on elevators. We use 10-24 cap screws with an allen head for low security places, aka no worries about tampering. For public parking decks, dorms and the like we use spanner tip screws that are countersunk flush. Other places get security tip Torx with the pin center, others get the cone drive things some fire alarm companies use, though they are a bit easy to strip.
