Max Payne is the first FPS that I can think of with a slo-mo mechanic, theres probably an earlier one than that though.
The Gamecube's joypad? Well, I do prefer the fire (Z) button on the Makopad 64, as I really don't like the placement of it on the Gamecube's controller. I also don't like the C-Stick on the Gamecube's joypad, but that's a lesser complaint of mine in a Makopad 64 vs Gamecube joypad, as I'm not fan of the N64's C - buttons really - they work fine (both on the Makopad 64 and the official N64 joypad), but I'd have prefered a second analogue stick to four face buttons if I'd have been in charge of designing the N64 pad. Overall, I would prefer the Makopad to the Gamecube's controller (though the latter is still largely great controller, and very comfortable to hold for long periods of time). Perfect Dark (N64, 2000, a year before the third person shooter Max Payne claimed to have introduced bullet time!) is the earliest FPS I can think of, although since Quake 3 and Unreal Tournament came out a year before PD, then either of those might sort of qualify. I say "sort of", since neither UT nor Q3 allow you to slow down time themselves, but modders might have added the ability, the same with Quake, Doom, etc. But PD is the first game, as far as I can remember, that has a slow-down-time feature as part of the retail game.
Requiem: Avenging Angel (1999) had bullet time. Pretty average game, but deserves a spot in this thread because using biblical plagues against enemies is pretty unusual.
Requiem: Avenging Angel introduced the time control on FPS genre in 1999, i'm pretty sure it was the first one. Amazingly uninspired and boring game but oh well. LOL: ^
You had to press a key to pick up ammunition in Breakdown, a very good XBox exclusive from 2004, that almost no one bothered with since it has one of the worst difficulty curves ever, it goes from hard to very hard to *****ing hard, to hard, to ****ing hard, etc. A real pity, as it's a very good game otherwise, it's a first person shooter where you never lose your first person view (it does it even better than Half-Life, as in Breakdown when you climb a ladder or shimmy along a horizontal ceiling pipe, or crouch through a small opening, you always see your hands as they do whatever they'd do in real life whilst you made those moves), it has very good (but hard) combat, more first person fighting (with *lots* of possible moves and counter moves) than weapon based, but there are guns you can use, an interesting story and atmosphere, and it's such a shame that (a) a sequel never arrived, and (b) the game was released with such a ridiculously unfair and variable difficulty curve. Jurassic Park: Trespasser (which I've never played, and I thought was just called Trespasser, I only found out differently when I went to check it's year of release on Wikipedia) is a PC game released in 1998, which I've always avoided as it's reputedly very bad, and also supposedly very difficult to get running right on non-Win9x PCs, but I had been told that you had to press multiple keys to pick up things, including, I imagine, ammunition. If so, then that's the earliest FPS I can think of where you have to press a button to pick up ammunition.
I enjoyed Breakdown. Well, until I got completely lost towards the end. It did get pretty damn difficult. Also confusing. That might have been one of the first FPS games to have the protagonists buy soda from a machine and actually consume it for health. It seemed as it tried to be a little Shenmue-esque.
No Rise of the Triad? Also, on Requiem: Avenging Angel, there's a level you have to carry another character on your shoulder.
Not totally sure but I think Duke Nukem 3D did that (giving you infinite money though). As for buying ammo from machines, the first one I can think of is "H.U.R.L.", predating Duke by a year.
I'm pretty sure (could be wrong though) that in Half-Life if you pressed USE (the PC key you'd defined as 'USE' in the game) on a vending machine, then you'd gain one health point. You could only do once for each button on the vending machine (there were about six buttons per machine), and I don't think you ever saw the soft drinks can emerge from the vending machine. I'm sure this was in Half-Life, but it might have been in a fan made mod rather than in the vanilla game.
Sorry, but Conker2012 is right. In half-life you can pres the use button on some vending machine to get a single hp, and you see the can fall at the bottom. [EDIT] Proof: http://youtu.be/9u1PUkqgVWA?t=1m21s
Your character (or their arm moreover) isn't seen grabbing the beverage and putting it to the screen (character's mouth) as to consume it though, right? It would just be an instantaneous health increase?
Yes, there is no first person view model animation of Gordon's hands putting a drink up to his mouth. Not even the second game has such animations for anything, & not many FPS have that at all. The Half-life 2 beta contains a weapon called the "Brick Bat." Basically, it was a weapon that allowed you to cycle through different physics objects that you'd pickup (Bricks, Head of a cremator (cut NPC), headcrab, etc.) & let's you throw them. This was neat in that it would show Gordon actually holding the damn things, but introduced problems for Valve. First of all, every item that they would intend for you to pickup for use with the Brick Bat weapon had to be modeled & animated individually alongside Gordon's first person hands, which wouldn't be a quick process. Also, the Source engine was pretty sloppy at handling decals then (bullet holes, paint splats, blood, etc), so if the item you picked up was scuffed it would magically appear normal. So what was the easiest & quickest solution? Making the +USE button hold up physics objects in front of you, but ditching any first person animations for it. It worked, but was not the direction they had wanted to go. That is where the gravity gun comes in. It's conception was perfect, as it allowed the player to "throw" physics objects without creating new first person models or animations, & covered up the fact that the object is still just floating in front of you with its design. Sorry, kinda off topic, but thought I'd throw it in since I personally love FPS' where the character does stuff in first person (drink, smoke a cig, eat a sandwich), which is why my Half-life 2 mod let's you do just that.
I believe it was the first to even feature different elevation levels, so sounds about right. edit: Spoke too soon, there was at least Ultima Underworld before that. Don't know if that featured any kind of elevators (doubtful, it being medieval and all... then again it's not really a first person shooter either.). There's also a Wikipedia article listing various innovators.
I think that would be a question of whether or not you consider U:U a FPS or a first person RPG. It might be splitting hairs, but I wouldn't put Skyrim in the same category as Wolfenstein. Unless I'm mistaken with what you're able to do in U:U.