Was Yesterday (CoD: MW2) - This mission first introduced slow-time events, specifically in the form of breach and clearing. This was the mission used to demo the then-new Xbox 360, and so you could play it in most tech shops on one of those caged in 360s with two protruding controllers.
The End of the Beginning (CoD: 2) - It's hard to imagine looking at the game now, but circa November, 2005, in Croydon's largest branch of PC World, this blew my mind and forced me to question everything I thought I knew about gaming.
