Achieve the following goals in Xbox Live to unlock the corresponding upgrade:

All six class medals: "Only veterans can handle this kind of language"
50 total kills: Avatar Pack II
500 total kills: Avatar Pack III
1,000 total kills: Avatar Pack IV
500 mobile unit kills: Bonus Avatar Pack

All six specialist medals: IR Enhance, Booster Plus, Quicker Tank Breech, Improved Hogster

2,000 healing points in the Specialist class: Enhanced Healing Speed
500 mine kills in the Specialist class: +1 Mine per loadout
500 backstabs in the Specialist class: Instant Detonate: Snoopa
500 fire damage kills in the Specialist class: Sinurator Tank Capacity Increased
500 Headshots in the Specialist class: Overcharge Power Boost
1,500 repair points in the Specialist class: Kinetic Seal, Increased Repair Efficiency
500 Marshals assassinated: +1 Primary Grenade Slot
500 Generals assassinated: +1 Secondary Grenade Slot
1,500 kills total: Projectile Color, Golden Bullets
3,000 kills total: Projectile Color, Regal Purple Bullets
4,000 kills total: Re-spawn Penalty Modifier 1/2 Reduction
1,000 VC Points: Hacking Device, Speed Chipped
Get 1,000 kills in the Long Ranger class: Steadier Aim, Nimbler Reload
Get 1,000 kills in the Sky Jockey class: Quicker Targeting, Quicker Breech
Get 1,000 kills in the Demolisher class: Increased Strayfur Clip, Guided Rocket Boost
Get 1,000 kills in the Thermophile class: Recharger Boost, Thermo Weapons
Get 1,000 kills in the Sneeker class: Snoopa, Improved Cloaking
Get 1,000 kills in the Grunt class: Clip Extension, Self-Heal Overcharge

To unlock Potty Mouth, beat Chapter X (Multiplayer Campaign).

In the area where the cheese farm is. Jump around towards the back wall and the B lightbulb will apear. Conker will turn into an anvil, break a wall and the tail there gives 10 extra lives.

To avoid ever losing the Bomb Run mission (according to the time limit), just enter a new area along the path of the designated point. Once you enter a new area, you'll experience a brief loading scene. Afterwards, you can quit game, re-load it, and you'll end up in that same area, along with a refreshed time. Repeat as necessary if you're running out of time.

To unlock Potty Mouth on multiplayer and Live, you must complete all three difficulties of Chapter X.

On part of the army campain, when you have played through the bunker and enter out side near the tank, get in the tank and start moving over the bridges. If you get hit in the tank and lose part of you life go into aim mode (click on move pad) shoot the floor twice and you will regain your health.