I beat Half-Life 2 a few days ago, and my opinion of it has not swayed. I hope to go through it again on a harder skill level or with cheats enabled or both. In the meantime, I have put in a few hours of multiplayer games and also began playing with , Valve's development kit and level editor. The program lets users create their own HL2, Counterstrike, or deathmatch levels, objects to fill the levels, or even entirely new games. So far my short time getting accustomed to the environment has yielded a two-room brick dungeon, a house façade, and a barren open air arena. Exceedingly simple stuff, but the potential is certainly there. My uninformed impression tells me the Steam engine has room for far more modification and expansion than Modders have taken advantage of. is just the beginning. As time goes on, players will see more physics-based objects like built into the levels.
Along those lines, the following are four mod ideas that I would like to see. Put a URL in the comments if any of them already exist. Note that these are not restricted to Half-Life 2. Some of the ideas could work for or another modifiable first person shooter.
1. Booby Trap World
This would be an arena filled with traps that players could set to catch other players. A hidden trap door would be the simplest: just a very thin skin that breaks or a door that swings down when a player walks across it. Perhaps players could move them around like the "portable holes" from that one Looney Tunes cartoon. The modder could make more complex objects like a gigantic mousetrap with an weapon or ammo box on the trigger. How about a swinging logs à la the Ewoks in Return of the Jedi? Falling cars from the Ravenholm level in the game?
Each participant could have his or her own bag of tricks to set before the match starts. They could spread the traps across the level and then drive the other participants them with gunfire. Players could diffuse traps or move them to catch the original setter. In Counterstrike, the traps could be used to protect the hostages or bomb target.
It would be difficult to prevent Booby Trap World from becoming very, very frustrating. There would have to be some incentive to prevent people from camping behind an impenetrable moat of booby traps. Perhaps diffusing a trap could be as easy as firing at it.
2. Sphere World
Does anyone remember ? I remember watching it as a small, small child. All I recall is that the main character, the Prince, lived on a tiny planet only about 20 or 30 feet across. Childhood memories aside, something like that would make a cool deathmatch level. The gravity would pull toward the center, so players could run around on the surface of the small planet, shooting bullets at each other that would travel tight orbits. Would the bullets "evaporate" before traveling all the way around the planet only to hit the shooter in the back or would the level get more and more cluttered with fast, orbiting satellites?
One could extend this idea to different surfaces. For example, World would have some bizarre bullet trajectories. Shell World, the inside of Sphere or Torus World, would have interesting sniping opportunities. What if one wanted to play on both the inside and outside of a surface? Then one could play on (in?) World.
3. The Mushroom Kingdom
The Mushroom Kingdom arena would have bright, pixelated textures with koopas and goombas running about. Players could throw Koopa shells using the gravity gun. One could shoot floating question mark boxes, and out would pop health or ammo. Stone boxes, on the other hand, would break and disappear, perhaps revealing secret power-ups. The modder could decrease gravity to allow for higher jumps. Team deathmatch uniforms would be red and green plumbers' overalls.
With the Mushroom Kingdom created, could be far behind?
4. Generated Level/Revolution Expansion
has had automatically generated dungeons for 20 years. I think time is ripe to make an automated level generator for a first person shooter. It could create a random section of City 17 filled with both Combine soldiers and revolutionaries. A player could join either side. The Revolution's object would be to take over that section of the city, while the Combine's would be to defend it. It could be modeled after Unreal Tournament's Onslaught mode and act as an expansion to the all-too-short revolution levels at the end of HL2. The difference would be that the terrain would be different every time. Either that, or the host server could regenerate a level after some number of rounds. That would let the participants become accustomed to the layout while still keeping it surprising.