Single-player FPS mods, especially ones that aren't brain-agony to play, are pretty few and far between. Adding plot, dialogue, setpieces and incentive to continue takes a lot more effort than making something that's a lot like Counter-Strike but with brown uniforms, after all. Never entirely comfortable with being shot at by strangers who are far better than me at placing bullets inside skulls though, I'm always on the lookout for a good soloplay homebrew effort.
The intruiging Minerva for Half-Life 2, for instance, is trying hard to tell a good story, and is doing far more efficient things with level design than Valve themselves. When covering it elsewhere, I did find that it had an unfortunate over-reliance on those Find The Door puzzles I despise so much. Happily, the developer popped up in the comments thread, not furious but cheerfully willing to take the constructive criticism onboard. (I really should have replied to him, but I'm forgetful, and a churl).
So, while waiting impatiently for the next installment, which, wonderfully, apparently has had Valve's own input on the puzzles, I stumbled across this. First Contact: Planetfall is a total conversion for Far Cry, created by the splendidly-named Sharkinacube, a team of students tasked to make a game for their final year coursework.
Well, I'd give them an A, anyway. While the understandable taint of amateurishness (there's some really infuriating bugs) weighs too heavy on Planetfall for it to be a commercial release, it doesn't undermine the quite incredible distance they've taken their mod from Far Cry. There's no way you'd guess what skeleton it was grown around if you didn't already know. The just-open-enough to feel lost but not actually get lost outdoor landscapes are there, but otherwise it's entirely its own entity.
Halo's a clear influence, from the music to elements of the HUD, and Metroid Prime, Outcast and Giants: Citizen Kabuto all get a look in too - most especially in the visual approach. Set on a thoroughly alien world, all the art is tailor-made and often gloriously wild. Sure, it's blocky and its animations are often crude or entirely absent, but when you're being followed about by a flock of impossibly cute, burbling, pink bunny-things, or being eyeballed nervously by a field full of otherworldly cows with emo fringes, nitpicking is irrelevant.
It's also trying really hard to be an adventure game (in the genuine rather than genre sense of the word) rather than a shooter. There is some shooting, and where there is it isn't very good, but largely it's about pushing ever-onwards by solving simple but thoughtful puzzles. Given a proper budget and more than six months, I'd absolutely love to see what these guys are capable of.
Perhaps most importantly, it features a giant flying whale.