MGS:
Solid Snake - "Liquid!"
Liquid Snake - "Did you like my sunglasses?"
Tekken 6:
Alisa Bosconovitch - "Hi, I'm Alisa. Now you must die."
Soul Calibur 4:
Algol - "This is the end, now fall!"
Street Fighter 4:
Ken - "Take this! Ora ora ora ora ora ora!... SHINRYUKEN!!"
Akuma - "Kako ma yoy ta! Isshun Sengeki! (beats guy up) Shun Gotsu, Messatsu!"
These look pretty weird but I like them and they got stuck in my head. There not even quotes, but still, if I had to pick a real one, I'd have to say in MGS3: "Ocelots are proud creatures. They prefer to hunt alone."(Ocelot, obviously)