Item description:

If you just use these saves it will unlock:

Stay Frosty - Marine on Hard
I Love the Corps - Marine on Nightmare

I admire its purity - Alien on Hard
Magnificent, Isn't It? - Alien on Nightmare

It Ain't No Man - Predator on Hard
One Ugly Mother - Predator on Nightmare

Game over man - Beat all 3 campaigns

All these unlock in order, you wont get the individual mission achievements so play through campaign before using these.

Just beat one mission on easy and all the above will unlock.

It will also unlock 10 spear kills, 10 headshot kills and 30 pistol kills if you get one kill with each of the required weapons.