Enemies always walk along strict pathways and never react if they lose contact with their comrades.
You can hang off ledges indefinitely.
Most people only have one thing to say to you, and they will say it repeatedly.
You are the chosen one. Everywhere.
No matter how good a shot you are, head shots are almost never fatal.
It doesn't matter how urgent the big bad is, there's always time to help out anyone and everyone you come across.
Ammo comes in big, glowing boxes.
Armour and additional clothing will always fit you, no matter how big or small you are.
...I have more, if you'd like 'em.