IronArcturus: Hostile Waters: Antaeus Rising - This is a 3rd-person perspective game where you can pilot multiple tanks and aircraft. It was very ahead of its time and should have had a sequel.
Indeed, it's a pity its gameplay wasn't used much afterwards.
IronArcturus: Rogue Trooper - In this game you play an alien super-soldier. It never got a sequel, but the gameplay was pretty good.
I don't know why but I really like that game, I even played through it twce after it was released on GOG after having already completed it twice before. My favourite part is unloading your gun as a turret, it was always very satisfying surprising your enemies that way.
Total Overdose: It's like a mexican GTA on crack. You have lots of weird power ups that added some fun to the gameplay.
Signal Ops: Rough around the edges but very unique gameplay. You control multiple characters with multiple "cameras" that have specific traits to perform certain solutions like the radio man that moves around an old school stationary radio, to a wrenchman (think burglar type) to a soldier and a spy. Very good atmosphere if you get into it, sadly I never finished it.
Project Eden: Again with the multiple characters but no multiple cameras, it felt more accessible than Signal Ops but no worse for that matter. Good atmosphere here too and while you end up pressing lots of levers and buttons it felt you were a detective team which I enjoyed, not too common in action oriented games.
Startopia: Some kind of alien management builder / society game that I have played way too little. I don't really remember anything specific other than that it had quirky mechanics that I liked. As I recal it's not too challenging, it's more of a relaxing experience. This seems to be more of a cult classic but appreciated by the people that found it but I think it's worth a mention so people can find it