APPLETURRET
Modus: It will just want to kill you. No beating around the bush.
How to avoid it: The usual way to deal with normal turrets. Would take more hits to kill as it is quite strong.

RARITURRET
Modus: Kills those who are not fashionable.
How to avoid it: Be well dressed and groomed and it will be far too busy complimenting you to kill you.

TWITURRET
Modus: Learns all it cans about enemies to kill it in the most efficient way possible with upgraded AI.
How to avoid it: Warn it GLaDOS will sent it back to turret kindergarden and watch it make normal turret mistakes in killing you rather than analytically defend itself.

PINKITURRET
Modus: Shoots sharp confetti and nitro-explosive balloons instead of regular bullets. Dark sense of humor.
How to avoid it: Laugh AT it, instead of WITH it. It will become too depressed to follow you.

RAINTURRET
Modus: Will kill you in the fastest way possible as soon as it sees you. Very fast moving.
How to avoid it: Challenge it to a contest. It will not back down. Make it a contest where it will inadventantly kill itself with a well-placed portal.

FLUTTURRET
Modus: Pacifist. It wants you as a friend and wants you to do the same, or else it kills you.
How to avoid it: Politely ask it if you can move ahead. It won't refuse a good-mannered friend.