What I have noticed with my cats is that when Fatman (my pmsing male) is irritated his tail flicks..umm whats the word....impatiently back and forth and its mostly just the tip of it! I also pay attention to his ears cuz when he is mad they start flicking and going back and I know hes about ready to chew someone out for bugging him. Now my other 2 get this casual wagging to their tails as if they are saying look at how pretty I am haha. I think if you watch your cats ears and eyes youll be able to tell better if its out of aggression or playfulness...
I'm a new "cat person" and one of the first things I learned was that cat tail wagging is WAY different than dog tail wagging.
When my cat plays (should I say on the RARE occasion that she plays) the tip of her tail will "switch" back and forth. And definitely when her ears are back and her pupils are large I know she's in no mood for affection.
But she will wag her WHOLE tail (sometimes) when I'm petting her and she's enjoying it. But I usually find that her tail wagging means she wants to be alone or wants to play.
The tails in this house are Members Of The Family. Tolly's Tail is used to communicate love and possessiveness. If he is near me his tail is wrapped around a part of me. Or he will walk next to me with his tail pressed against my leg.
Mazy's keeps me in laughter as it is so expressive and responds to every little stimulus in very hilarious ways. She has a funny way of holding it in a hump (see 3rd pic 2nd row) and waving it in all sorts of ways, while being held in that position. Her tail never stops moving.
Jennie's Tail is a very quiet individual.
One of my favorite things to do is to sit quietly and speak to each cat in turn, just to see the tails rattle.
"Mazy" I'll say and just the tip will rattle. Mazy. A bigger rattle. But if I keep on with it, soon I've got a fully lashing wiggling thumping Tail. heehee
Riley's tail is very long and heavy so he almost never lifts it up. Most of the time it drags the ground like a dust mop. If he is slightly irritated he will twitch the end of it a bit. If he's mad he flops the whole thing up and down really hard, lol. He does swish it side to side a bit when he's about to pounce on something.