i can game all day 

1) it means fuck all day; or,

2) generally do anything all day, which (when you generally do anything all day) usually means fuck all day.

common usage:

girl: "so wha u wanna do? i can game all day"
boy: "idk scout how bout we take em out..."
girl: "when and where but always ben"
boy: yup

i can game all day by darkcloudhorizing June 5, 2013