Design a new game mechanic

[Uber Evil]

An RTS game where after fighting an opponent and crushing their army, your army can then pick up their weapons and supplies that go into your resources. Im not sure if a game like that already exists.

Mount and Blade my good man. Except I guess that isn't so much an RTS, as a first person fighter.

 

[Savagezion]

Mine is in simulation. Since there are basically no good Theme Park style games out there anymore with the whole Chris Sawyer debacle, I wish the source code for RCT3 would be released. (I ain't holding my breath dont worry.) But I would make a mechanic that makes the people a little more interesting walking around your park. First you would have to slow down time progression a bit. As well I would pull in the system from Bullfrog's Theme Park where you purchase parks in regions. Each region would be assigned attributes that would effect how interested in your park they are. Some regions would not have a large rollercoaster interest but instead enjoy thrill rides etc.
Anyways, that is a little sidetracked to my original idea. By slowing down time the guest and revenue management would get a little more interesting. I personally would actually slow it down so that 1 hour of gameplay is a week. It uses 1 day/night cycle and you set up shows and games in an "intermission" screen in between weeks. The local population would grow tired of certain shows, rides, etc. However, once every 20 weeks (year cycle) a ride, show, etc. has a chance of becoming a trademarks of your park. If a trademark shows up, it will bring in a steady flow of regional customers and tourists as well.
Now that I think about it I have quit a few mechanics I would throw in to a theme park simulation. Chris Sawyers rollercoaster design system was just awesome though. Not sure what the restrictions for that is exactly. But I have often thought that if I ever got into game development this would be a game I would want to pursue. The locals would additionally, steal, fight, sue you for ride accidents whem on them where you could choose to settle out of court or see it through, etc.

 

[TsunamiWombat]

I came up with a system for magic usage when I was a kid, and I've still yet to see any game come close to how I designed it. Only game even remotely close was Dragon Age having some sembleance of spell combos, though they were almost exclusively area of effect spell stacking. Part of the system I had allowed for on the fly spell casting combos to create new effects. An example, spellweave Slow and Fire together to create Immolate, which instead of being a single fire blast turned into a fire damage over time. This is the simplest and easiest to understand example, I had one for basically any combination of spells the player could come up with.

There is more nuance to it, like a scale of magnitude based on how much it cost to cast and more, altering the base spell or combo effect.

Crusader of Centy did something similar on the Genesis (SNES?)