I guess I will start with....
Happy noises:
Ppppprrrrrrrrrr Ppppprrrrrrrr with no actual vocal input means "I am happy to be near you, on you, pressing on your bladder, sitting on your head, basking in the warmth of your body."
Ppppprrrrrrrrrr Ppppprrrrrrrr with no actual vocal input but accompanied by drooling means "Yes! Yes! Yes! Aaaaah, ecstasy!!!"
Ppppprrrrrrrrrr Ppppprrrrrrrr also means "Gee, thanks for refilling my bowl."
Ppppprrrrrrrrrr Ppppprrrrrrrr can also means "I don't feel good, but you are here now and will help me feel better."
A variation:
Ppppprrrrrrrrrr Ppppprrrrrrrr at the same time as a slightly drawn out rising Rrrrrow means "Come here, my love."
Useful conversational phrases:
Mew in a very quiet voice either means "I'm here." Or it means "Mommy?"
Rrrrow said in a rising tone while walking through a room means "Are you here?"
The same Rrrrow coupled with an intense stare means "Can I sit on you?" Or "Why are you sitting in a large porcelain container of water?"
Mmmmmrrrrow can mean the same thing.
MMMMMRRRROOOWWWW however means "Look what I caught!"
Wow Wow Wow Wow Wow!!!! is another version with more emphasis, as in "Look what I caught, look-it, look-it, look-it!!! I am soooo good!!!"
MMMMMph!!! means "Look what I caught - I can't let go of it or it is going to get away and run across your bare feet!"
MMMMMRRRROOOWWWW MMMMMRRRROOOWWWW MMMMMRRRROOOWWWW repeated regularly and allowed to slide down the scale and then back up, coupled with an unusual posture means "Come up and see me, big boy!" or "I AM IN HEAT!"
WOW!! Bam! means "I'VE HAD ENOUGH - BACK OFF!"
Meeeee-out!!! (also spelled Meeee-owt) means "Open the door, I need to go out." It also means "Open the door, I need to come in."
Sniff-sniff-sniff means "What IS this? I am going to roll in it because I find it intoxicating."
Huff-huff-huff is also called "Flehming" and means "I smell something....somewhere....what is it....maybe it's fish....maybe something.....I don't know but it is interesting...."
Ik-ik-ik-ik-ik-ik said very rapidly means "There's a bird out there - Kill! Kill! Kill!"
Negative emotions and expressions of dislike or disdain:
Sniff-sniff-sniff coupled with scraping motions of the front paw on the floor means "This stinks like s**t. I need to bury it." However, there are various intents - it can mean "I need to bury it because it IS s**t." or "...because it is too good to share so I need to HIDE it." or even "...because it is yours and I think YOU are s**t." The last phrase is usually directed towards a member of the canine fraternity.
Psssssssssssssssssssssst! means 'Unless you want to be a blood donor, don't make me get down." It can also mean "You smell like a veterinarian!"
RRRRRRRRRRRRRRRrrrrrrooowwrrrrr!!! means "Prepare to die!"
Cccccchhhhhhhhh!!!!!!! (pronounced as the Hebrew Chai) means "You are dead, Mo-fo!" This is usually accompanied with flat ears, extended claws, a wrinkled face, and a crouching posture designed to let the speaker leap high enough to slit the antagonist's throat.
RRRRRRRRRRRRRRRrrrrrrooowwrrrrr Cccccchhhhhhhhhtttt!!! means "Take that, you evil canine excuse for a fur coat on feet!!!!"
OOooooooh Nooooooo!!! OOOOOrange Ccccaaaat! is a phrase used by only one cat of my acquaintance and means "Go away, other cat that lives in my house, go away, please!!!"
And last but not least...
The Silent Meow
Absolutely silent but a full, open mouth meow aimed directly at the cat's person means "Please.....I will die if you don't do this for me....please....I am getting faint...please?" Or "Please.....I will die if you don't feed me that morsel you are about to gulp down....please....I am getting faint...please?"