Let me amend my statement. I would really love to go somewhere in Africa, like Zimbabwe or the Congo or something, really get a jungle/tribal vibe juxtaposed with sleek, cold Combine technology. I want to see squads of malequipped CPs blunder their way into ambushes and traps, OTA skulls hanging from trees, vortigaunts that haven't even learned English yet and who have actually formed a tribe again, teeming Xen wildlife, the established cities in a constant battle with the outside environment.. There's an absolutely fantastic event to be built around that, if only there was a suitable map. It's the only setting that hasn't really been done imo.
Of course the main reason that's not my first proper choice is because you'd have idiots screaming about da wae and watermelons and constantly doing racist shit.
That's my random thoughts anyway, have a good gut feeling about this event x