The ability to turn of/on certain weapons with keys

[JonZ]

 this would add effect to anything that uses a surprise element in something like a multi-player arena, with real people, who can be surprised.

[Nekoatl]

This ability already exists, and you can customize the behavior any way you want using logic parts.  Granted, use of logic parts can quickly become unwieldy, expensive to deploy, and time consuming to construct, but it's still possible.  Though, I'm not sure how much of a surprise having some of your weapons turned off would be, at least once they see your drone, since you can't make parts invisible....