I don't know how many of you ever heard of the
Retribution Engine
Basically it's like a free version of FPS Creator to me but can do certain thing's better, the AI feel's more compentent, you can make your own weapon's easily from a simple pistol to a rocket launcher and grenade launcher's, the map editor feels more creative then just placing boxes as walls, the map editor can be compared to Hammer, Valves level editor for their games, easy to use and makes more creative levels easier and similar interface.
You can also make terrains and water, terrain using terragen or some terrain image generator and water is as easy as placing a cube and set it's properties to water, you can make costum enemies easily as well allies or simple civilians, you can set them trough triggers so they will appear once you done an objective. (think about an enemy assault appears when you go back after doing an objective?)
The models it supports are md2/Quake 2 format however, the game comes with 3 full episodes (1 episode left unfinished) and many single levels to play as well as challenge levels like survival mode and time attack mode levels.
Forgot to mention it needs no programming or coding to use, you script cut-scenes and triggers trough the map editor, it's too easy really.
There might probably some other things I forgot to mention but the program is also final and is no longer supported however, such a shame really.
That's not to say FPSC is complete garbage really, FPSC has network play, a more powerful engine (retrib is similar to that of Quake 2 or half-life 1) and also quite easy to use and some even sold games with FPSC from what I read but I do hope FPSC will improve on these things however, I tried FPSC for a small time and when I played some of it's demo maps the AI ticked me off as well as I saw some youtube videos of FPSC games in action, most were crap (specifically Mirrors Edge fan remake) some were done well like "drugs kill" game.
Another thing I like about FPSC are the huge set of model packs, either way I might retry FPSC sometime in the future when it is improved alot, possibly there might be an FPSC 2 in the future with a load of improvements and a better map editor that doesn't feel like sticking lego blocks but more advanced level editing? I'l look forward to it.