Here are some of them.
The 'play with me (or die)'
Mouth is very good at looking cute when he wants something. He lets out this odd little two-part brrrrrrp, generally while patting my knee or face with his paw. He's like an excited child putting his hand up in class. "Pick me, Miss! Oh, me! Oh, I know the answer! PLEASE Miss!"
Usually when he does this, he wants me to wiggle his aerial about for him.
If he doesn't get what he wants, he can transform instantly into a terrifying hellbeast.
The 'where are you?'
When I'm not around, my boyfriend tells me Mouth wanders around the house listlessly, occasionally emitting forlorn miaows.
His miaows have never been melodious, but this one is particularly ridiculous. It starts off all waily, but then he seems to remember he is a cat and tries to surreptitiously convert his wail into a cat sound.
Possibly his mother was a banshee.
The 'THERE IS A BIRD THERE IS A BIRD THERE IS A BIRD'
Like most cats, Mouth and Tail make weird chattery noises when there is a Thing that they want to eat.
Traditionally it's a bird (Tail excels at bird-chattery), but I have caught Mouth chattering at wholly un-chatter-worthy things like woodlice and fluff.
Tail's chatters are superb. I'm convinced she is skilled in ventriloquy and a qualified voice projection instructor. Even through double-glazed glass, they make sparrows at the other end of the garden quake with fear.
Mouth's are rubbish. They sound like a broken power drill. Woodlice flock to my house purely for the entertainment.
This is the feline equivalent of a toddler stamping its foot and throwing a tantrum.
When Mouth and Tail have a stand-off - usually because Mouth has muscled in on Tail's dinner, although once it happened because he sneezed on her bottom - growling inevitably ensues.
They always make up afterwards. Mouth is a master of the Apologetic Ear Groom.
The 'service announcement'
This is my favourite cat noise, and a peculiarity of Tail's.
Whenever she's about to do something she feels I should know about, like jump onto the bookcase, she gives a little chirrup.
It's very courteous.