There are four different ranks you can achieve in Star Wars Battlefront II with each consecutive rank requiring a certain amount of medals to unlock.
Your rank will determine how many ai units will follow you with the command button.

Private: 1 Unit (20 medals)

Sergeant: 2 Units (21 - 99 medals)

Captain: 3 Units (100 - 299 medals)

General: 4 Units (300+ medals)

You can obtain "Awards" in game by filling certain requirements.
Different medals will award you with unique bonuses such as better weapons or player buffs.
Depending how many times you've received a singular type of medal will affect its "rank".

These ranks are:
0 - 3 Green (No bonus received at this rank)
4 - 31 Veteran (Bonus is received)
32 - 63 Elite (Award criteria is lowered)
64+ Legendary (Bonus is given at the start of the match and lasts for the entire duration of the battle)

The Awards
Endurance
Get 12 points in 1 life (9 for Elite)
Energy Regeneration Bonus: Makes your stamina bar fill up faster.

Guardian
Get 24 points in one life (18 for Elite)
Damage Reduction Bonus: Decreases the amount of damage you will receive. Shown by a blue spherical hue surrounding your character.

War Hero
Get 36 points in one life (27 for Elite)
Increased Damage Bonus: Gives the player an increased damage buff. Pretty self-explanatory really. Shown by red lightning bolts emanating from the player.

Frenzy
12 kills with blaster rifle in one life (9 for Elite) Elite Rifle: A very high damage rifle that kills quickly more so than the regular blaster rifle. Fires in a 3-round burst with purple blaster bolts.

Marksman
6 Headshots with Sniper Rifles in one life (4 for Elite)
Beam Rifle: Higher damage and will penetrate through units. Considerably less ammo and smaller magazine.

Demolition
4 Rocket Launcher critical hits in one life (3 for Elite)
Remote Rocket Launcher: Fires a rocket that you get to control, steering it is the same as your starfighter controls. Can boost and deals more damage when doing so.

Regulator
8 Kills with Shotgun in one life (6 for Elite)
Flechette Shotgun: A shotgun with higher and more concentrated shots. Fires purple bolts and since the shot grouping is tighter you can fire it from just a little bit further away.

Gunslinger
6 kills with Blaster Pistol in one life (4 for Elite)
Precision Pistol: Deals way higher damage than the regular blaster pistol (approx 2-3 shots or a one tap to the head). Unlike the regular pistol it also has a limited amount of ammo. Fast firing rate, pretty much as fast as you can mash the shoot button. Purple bolts too.

Technician
Slice a vehicle with Fusion Cutter
Vehicle Regeneration Bonus: Vehicle regenerates health like the pilot/engineer class.
Applies to all vehicles including on the ground and not just space battles.

The old cheat codes seem to work in the Classic Collection which is pretty cool.

Enter them in the pause menu and use the 'D-Pad' if you're using controller or the 'Arrow Keys' on your keyboard, you will know if the code was input correctly if you hear a chime. For some reason though they reset after each match so you'll have to re-input them every game.

Star Wars Battlefront II

Infinite Ammo
Up, Down, Left, Down, Down, Left, Down, Down, Left, Down, Down, Down, Left, Right

Invincibility
Up, Up, Up, Left, Down, Down, Down, Left, Up, Up, Up, Left, Right

Disable HUD
Up, Up, Up, Up, Left, Up, Up, Down, Left, Down, Up, Up, Left, Right

Low-Res Character Models: Character models become low poly, very basic detail and some become stretched. Looks pretty funny sometimes.
Down, Down, Down, Up, Up, Left, Down, Down, Down, Down, Down, Left, Up, Up, Up, Left, Right

Comic Book Captions: Only used in Hunt mode with Wampas [Hoth and Rhen Var]. When you make an attack with the Wampa it will generate comic style hit effects.
Up, Down, Left, Down, Left, Right

Alternative Sound Effects: Makes everything sound like its underwater is the best way I can explain this one, Kinda meh in my opinion.
Up, Up, Up, Left, Up, Down, Up, Up, Left, Down, Down, Down, Left, Up, Down, Down, Left, Right

Star Wars Battlefront I

If you make a profile named "Jub Jub", all characters will become squished to the height of an ewok which is rather comedic.