I agree with anything from Portal 2 because it is by default the most hilarious gathering of quotes ever.

I haven't played it (I plan to eventually) but I saw a video and the Far Cry 3: Blood Dragon tutorial bit is amazing. Examples include...
Loading basic tutorial batch 101 from “Military Navigation for Idiots
Press ‘Enter’ to Demonstrate Your Ability to Read
Jump if you wish to jump
Pressing ‘Space’ enables you to move in a Z-axis arc without touching the ground in between
Moving allows you to go in many exciting directions
Running is like walking — only faster
Are these tutorials getting in the way of your mayhem?
etc. etc.

I like a lot of the Uncharted 2/3 commentary, too (particularly between Nate/Sully and Nate/Chloe), although I can't remember it off the top of my head. Also, from Sazh: "All this dampness is damp." Gets me every time.