[patmcc]

If you live in a jurisdiction with good labour laws, your boss might be able to fire you "on the spot" but they'll still have to pay at least 2 weeks of severance.

Also, keep in mind that leaving immediately might seem like it hurts your boss and/or the company, but more likely it just stresses out your co-workers who have to pick up where you left off without any help. 2 weeks to hand off all your current stuff makes their lives a lot easier.