So, you’re still unsure where you’re going to buy The Master Chief Collection from. Quite a predicament, indeed, since there are many options. Luckily, I was informed of the bonus pre-order skull that you get based on where you pre-order the game from! Here is the list, and hopefully it will help your decision!
Bandana Skull (GameStop) – Unlimited Ammo and Grenades
Grunt Funeral (Best Buy) – Grunts explode upon death
Piñata (Amazon) – Enemies drop Plasma Grenades after every melee attack
Boom (Microsoft Store) – 2x explosion physics
Bonded Pair (ShopTo) – You get a 100% damage boost for 60 seconds if your co-op partner dies
Special thanks to TORRESEL16 and dvrgameclips for the suggestion and information.