Bonus level  -  Successfully complete story mode to unlock a bonus "infinite" level.
Unlock Armour  -  Defeate bosses in the infinity sector to unlock armour

How to Unlock
Blast Helm Defeate lvl 50 boss - Enforcer
Surge Helm Defete lvl 40 boss - Mantis

Unlock Weapons  -  These weapon drops when you kill the boss.

Inferno weapon  -  Defeat Colossus (Sector 2 Base Boss) to get the Inferno weapon.

Quick reload  -  Start to reload then switch to a different weapon. Switch back and your weapon will be reloaded.

Full Health  -  Go to the pause menu and hold L+R and press up, down, left, right, x, square and then press pause and you should have full health.

How to Unlock

Copperhead Beat Sector 2 Ruins Boss - Mantis
Inferno Beat Sector 2 Base boss - Colossus
Judgement Beat Sector 2 City boss - Enforcer
Neutron Gun Beat the boss on Infinity mode level 30
Onslaught Beat the boss on Infinity mode level 10
Trident Beat the boss on Infinity mode level 60
Vulcan Beat the boss on Infinity mode level 20