I will be working on a headcrab factory/ canister manufacturing plant. Not the most original idea but it appeals to me and should be some fun.
Ideas so far -
*Gordon arrives via teleportation
*Most of the facility is underground (You will probably only see the surface through a few holes
*The facility is possibly overrun, the Combine have no control over it anymore
*Gameplay could involve having no weapons (or very limited ammo and weapons), just the HEV suit, while having to avoid hazards and headcrabs
*Main objective will be to get to the surface, where the teleporter can regain signal strength or something (not sure how kleiner's teleporter works in HL2)