William "B.J." Blazkowicz v1

Adds in Wolfenstein 3D's protagonist as a playable character.
Automatic playstyle and Ringslinger modes are not supported.

Controls:
Fire: Shoot
1-4/Next Weapon/Prev Weapon: Switches weapons
Spin: Toggles autorun (Only when on the ground)

Features:
Looking up/down
B.J. is unable to look up or down, instead stuck looking straight forwards. If you need to take a look around, switch to third person to do so. Despite this however, B.J.'s attacks will manage to hit an enemy no matter how high or low they are as long as it's a straight shot.

Autorun
With his instant movement, precise platforming isn't very easy for B.J. to do, however by pressing the Spin button while on the ground you can toggle Autorun off and move at a much slower controllable speed. Combine this with third person for an easier time with platforming.

Weapons
B.J. has a couple of weapons in his arsenal, though he'll only start out with a pistol and knife, the Machine Gun and Chaingun can be found throughout levels. However if you die you'll lose the extras and have to collect them again.

Pickups
You'll find a few helpful items around, walk into them to pick them up.
Ammo: Dropped by enemies, gives four ammo on pickup.
1-Up: Replaces 1-Up monitors, gives you an extra life and fully heals you.
Medkits: Replaces most ring monitors, heals 25 health on pickup.
Weapons: Replaces a smaller amount of ring monitors, lets you acquire the Machine Gun and Chaingun.

Health
Rings are useless for B.J. outside of score, instead he has his own health that'll go down every time he gets hurt and that damage will carry on over to the next stage, seek out medkits to heal yourself, or pick up a 1-Up to fully heal.

Chaos Emeralds
However if you don't want to keep recollecting weapons every time you die, you could always collect the Chaos Emeralds. Every one you collect will increase your starting ammo by 6, three emeralds lets you always have the Machine Gun and all seven will add the Chaingun to that too.

Additionally to help B.J. complete some levels:
Weapons can break bustable walls, the knife is also able to break spikes.
Bustable floors will break the moment B.J. steps onto them.
If you have less ammo than the starting amount, you'll be given some extra on the next stage to make sure you can beat boss stages.

Credits:
Me - Code
id Software - Wolfenstein 3D
PSTrooper - Posted recordings of the PC Speaker sounds on the ZDoom Forums
Terra - Multiplayer Playtesting & Feedback
Mason - B.J. Sprites, taken (and edited slightly) from here (Thanks to Lightdasher too for pointing me to these)