The PA system can be a useful means of addressing characters in the right game settings. Consider its role in the classic TV comedy M*A*S*H - the PA announcements were virtually a character unto themselves.

The game Paranoia has The Computer, of course, which plays a similar sort of "voice from above" role that interacts with the PCs. But you could also incorporate it into other genres. Imagine a PA system making announcements at a passenger spaceflight terminal, or on board a long-haul cruise vessel when things start to go mysteriously bizarre. Or on a space station.

Or in the streets of London on an otherwise normal contemporary day...

Transcript

PA System: Attention all personnel! A group of tourists has arrived. Please ensure your work stations are tidy.
[SFX]: klik
Tàrkin: {into intercom} And nobody mention Naboo.
PA System: Right, what the Governor said.
PA System Voice 2: {small} What about Naboo?
Tàrkin: Lord Vader, Ah want you to 'andle zis. You are always so good with ze... 'ow you say? Public relations.
{beat}
Tàrkin: Trah not to kill any of zem.
{beat}
Darth Vader: They will receive a suitable welcome.
PA System: By the way: All shore leave on Naboo has been cancelled until further notice.