Cpt. Macmillan
Aside from Gaz he is the best character in Modern Warfare 2. He appers twice in the game when Cpt. Price is having a flashback of 15 years ago. All Ghillied-Up and One Shot, One Kill are the missions in which you play as Price.
Cpt. Macmillan quotes:
"Shite! Where did he come from?"
"Pooch doesn't look too friendly."
"Are you daft?"
"The word stealth doesn't mean much to you does it?"