From Gears of War, Call of Duty etc. I learned that bullet wounds aren't actually all that serious and can infact be sorted out by hiding behind a stack of crates or a low wall.
From Fable 2 I learned that consuming so much as a single pie/mug of beer/piece of meat will instantly cause you to put on noticeable weight.....I stick to celery these days thank you very much.
From Portal I learned that any and all cake you may come across in life is in fact, a lie.
From GTA4 I learned the true horror of having a mobile phone.