I’m gonna go with Albert Schweitzer’s answer: music and cats.
Sheets dried on the clothesline in the summer sun.
A great glass of Tempranillo or a white Rioja.
A How I Met Your Mother Marathon.
A day of thrift shopping and/or flea markets and/or antique stores with my husband.
The sound of my husband really, solidly laughing (I don’t think I’m breaking the rules… I didn’t say him per se, but his laughing.)
Spending time in the natural world
Driving down an open road
Paris
My kittehs
Anything containing chocolate and peanut butter
Oral sex
Rachmaninoff
On that note:
[ol]
[li]People who don’t threadshit[/li][li]The New York Yankees[/li][li]The sound of sleigh bells[/li][li]Music[/li][li]Lazy days lying in the sun[/li][/ol]
Music
Sex
Chocolate
Laughing
Flying.
sigh Mortgage, car payment… 
Camping.
Sleeping (or not sleeping) in a watertight tent, during a thunderstorm, with someone I love.
Baseball.
Going to a concert.
Crawling into a warm bed on a cold night after a long day.
Dogs
(and other stuff but nothing really comes close to the joy from dogs)
sweatshirts
my puppy Zen
snow crabs
Muscle of Love CD
drab green
Libraries
Hey! Who said you could have six? 
Those are great ones! Specially babies laughing, and cut grass, and kittens, and …
It was actually sort of sweet and romantic, but had THE most idiotic ending.
My puppies snuggling with me.
A roaring fire in my fireplace.
Thunderstorms.
Dissecting things.
Lemon Heads.
Flying my glider
Body surfing
Fresh powder
Rafting the Grand Canyon
Music
What, no long walks on the beach, or romantic candlelight dinners? I knew it!
Sleep
Beer
Spicy food
Documentaries
Hot summer days
A nice breeze on a warm day
Sleeping in, snuggled under a warm blanket
Kittens
Fresh-baked bread
Walking out of work or school on the last day before a long vacation.
A quiet house on a grey fall day, when everybody is napping or reading.
The smell of the ice at the hockey rink.
Rush concerts.
Tex-mex.
My kids giggles.
Coffee
Surfing
Wine
Sex
A Good Book
In a curious two-fer, this post comes pretty close to describing a perfect day as well.
Warm spring day, when the sun is shining, the birds are singing, and everything is greening up
Horses
Cats
Snuggling in a warm comfy bed with a good book
A delicious home-cooked meal