The Spy: Gentlemen...
Key Roles: Sappin' Sentries, Stabbin' Suckers
Best For: Smug bastards who enjoy ruining someone's day
You probably think you're pretty clever, don't you? I bet you do. That's why you want to play as The Spy, you pretentious jerk. Yeah, you sneak around the battlefield, fooling medics into healing you and stabbing people in the back, but that doesn't give you an excuse to be so god-damned self-congratulatory. Why don't you take a break from touting your greatness for a minute and go take care of that sentry, The Scout's died a couple dozen times while you were patting yourself on the back.
Because the Cloak and Dagger invisibility unit is motion sensitive, you can stay unseen as long as you want provided you don't move. Creep across the battlefield and lay in waiting deep within the enemy base before using Your Eternal Reward to stab them in the back and assume their identity. If things go south, pull out your Ambassador and put a slug in their head, it's a guaranteed critical if you hit.
That Engineer thinks he's pretty hot shit. It's time to ruin his day. Use your standard Disguise Kit to blend into the scene before placing a Sapper on his sentry. Every building you destroy earns you 1 critical hit with the Diamondback, and should you expend all your lucky bullets before escaping, the Dead Ringer will throw them off your scent with by deploying a dead decoy.