As many people have stated, for the most part, our add-ons are 50 variations of the same goddamn gun, with maybe single digit differences in the code, and a different model.
Really, the only major difference is that one is prettier.
Sometimes, someone incorporates something fancy into their add-on, such as Bushi's putting in a laser sight for the .880. But otherwise, it's all the same monotony.
Right off the top of my head, the following are what I recall as fully original add-ons:
1. Invisiilty Watches
2. Laser Pointer
3. JVS System and Related
4. Rotondo's L4B
5. The Carrier Vehicle, primarily because you can walk on it.
6. Hat Mod
7. Sub Events
8. LSG (Even though it broke; I think)
Now, in comparison to some other games, such as Cortex Command (They're all guns to some extent, the game being what it is, but they do a whole lot more):
1. Particle Accelerator
2. Behemoth
3. Hookshot
4. The Reject campaign remake (Basically a campaign level that was completely remade)
5. All Mannable Vehicles; Considering the game normally didn't do that in the first place
6. CCRPG
7. Cash4Kills system
8. Gravity Guns
9. Growth Pods
10. Jericho Missile
11. Zombie Infection system
12. Control Room
So, in comparison to most other add-on capable games, we're a bit pitiful.
Now, of course, CC was made without a commercial engine (I think) and use Lua, rather than Torque, so of course there are differences in limitations, but nonetheless, I'm sure we can do a whole lot more.