I think a dualshock 4 would be good for you. It needs a program called InputMapper, which allows you to remap all the buttons and allot of other things.

I can't recall any fps that doesn't have a "next weapon" and "previous weapon" key.

I disagree, i would never recommend it to anyone considering there is better alternatives in the market.

- The analogs sticks will wear out quickly;
- There are some problems with the triggers not registering completly the pressure (ex. in driving games you should go up to 160KH but it only registers 130KH) and also sticky bumpers;
- Expensive.

The worst thing that PS4 has is definitely the controller, besides the cheap material, it's expensive because of the dumb stuff that no one wants (touchpad, light and the speaker).

I would rather recommend the xbox 360 controller even with the terrible dpad (i think they fixed that later).

Dunno, it was more of a "just in case" situation, guess that he just needs to remap those to the bumpers and he is all set.

You don't need to log in to Steam to use it in "Desktop Mode" (a single - configurable - profile for all games). You do need to run the client though. Logging in lets you sync configurations and maintain your library.

I realize that they're on the expensive side, but if you're interested in seeing something more specialized you may want to look at the examples at these links:
http://www.oneswitch.org.uk/1/AGS/AGS-bespoke.htm
http://rjcooper.com/game-controller/

No one controller will work for everything because some games just don't support controllers, To get around that issue, I use:

1. Xbox 360 controller
2. Xpadder (It's a program that lets you assign keyboard and mouse controls to a controller.) There are other similar types of programs out there. I've found Xpadder to be the easiest to use though.

I believe Xpadder works with other types of controllers too.

Wow, you guys are really awesome with all this help.
Got to play with an X-Box 1 controller at Best Buy yesterday. It was hooked up to a Lego game.Felt comfortable operating it. The only buttons I couldn't access were the one(s) in the back, left. The left thumb felt comfortable moving around.
This could actually work very nicely if paired with a program as suggested by Hudfreegamer.
Tell me: Do any of these programs have the ability to bind a key plus the shift key? Slow for me even when I had all fingers operational LOL.
Scartch...

Just FYI, best gamer I ever met was a guy born with just two fingers on his right hand. Mother fucker was no fun to play against he was too good!!! :P

Are those big buzzers buttons for the feet?
I'd very much like to have buttons for my feet and always wonder why I never see such things since all your fingers are racing among buttons but the feet aren't used at all.
I'm no organist, but I could handle a few buttons under the table.

I imagine for the same reason that people have had to mod their xbox pads in a similar manner to those in ValamirCleaver links so that there are buttons where your fingers are on pads e.g https://youtu.be/UxN_rrwIA1g?t=3m44s

The PS4 pad has the best features for PC gaming i.e the touchpad,motion sensing and you can get mini bluetooth keyboards which fit onto it like this one I found.
http://www.lightinthebox.com/bluetooth-mini-wireless-chatpad-text-chat-message-game-controller-keyboard-console-for-sony-playstation-ps4-controller_p2850178.html

Uhm, and where would you use those features? I mean, if you can use the touchpad as the mouse pointer for games like System Shock 2 (inventory) then yeah, otherwise i don't see much use for it. Hell, those features are barely used on PS4 games unless they're made by Sony Devs studios (still gimmicks)...

You would use it for anything you wanted to.
An example of a game which would use it's extra features would by something like this.
http://www.gog.com/game/il_2_sturmovik_1946

I'm not sure if the Xbox One controller will work with Xpadder. Does anyone know?

The Xbox One controller is supposedly supported on Windows 10 and a driver is available for Windows 7 & 8, but I recommend the wired xbox 360 controller. That's what I use and I know it works.

Besides, I still use Windows XP and the Xbox One controller isn't supported.

I have a Logitech F310 and they're solid game pads. Dunno how well it would work for you with your constraints though, you'd probably have to do trial and error.

Do you have any friends/acquaintances that are propeller-heads with any background in electronics and tinkering? If so, you might be able to get someone to either modify a controller customized to your disability or make one completely from scratch, possibly even using a 3D printer to make parts. If you don't know anyone that might be able to do this, you might even consider searching online for forums where people do or might be interested in doing such things. I don't know of any off hand, but I'm sure there are people out there who would love to help out. I've seen articles where people made custom 3D printed plastic beak for a bird that had its beak ripped off and all kinds of similar stories both with humans and animals so the wisdom and enthusiasm is out there for sure.

Hope this helps. Crap, the Steam controller is a fantastic idea. Dunno why that never occurred to me at first thought. I have not used one yet but have heard nothing but good things about them overall and they're only around $60.

http://www.slashgear.com/steam-controller-configured-to-allow-disabled-gamer-play-skyrim-with-one-hand-13414465/