My Himalayan cat. He is SO beautiful my heart gives a tiny leap of joy every time I look at that gorgeous creature.
The dark shapes of trees in the fall and winter outlined against the sky. I will stand there like a loon, staring up into the sky.
Mosaics
Palm trees
The Smothered Mate
The south-west Durham Dales (my home of years past)
Loads of others here that I’d agree with as well but a lot of the suggestions remind me of something I’ve often wondered.
In the ever-present "“what is art” debate I often think that what “good” or “successful” art does is to give the observer an equivalent emotional response that we get from nature or natural phenomenon. Perhaps art exists at the junction of nature and man? Is that too poncy?
A good example would be dry stone walls. Someone already mentioned them and I’d agree they are beautiful and the best ones are truly sculptural. Or mosaics? what are they other than a human attempt at butterfly wings and snakeskins?
A debate for another time maybe (I’m sure it’ll be back!)
Everything I’ve seen from the Hubble telescope.
FWIW, Antoni Gaudí agreed with you.
Streets paved with pebbles. A bitch to walk on in thin soles, a neckbreaker in high heels, but I can get lost in time just following the patterns.
Fine company indeed, I do love his work.
One more I thought of, Romanesco broccoli.
Mandelbrot fractals…Jeep Grand Wagoners…
Major 7 chords (Todd Rundgren)…certain types of armor from the late 16th century that have etched and gilded decorations…
The shade of brown on a conker(horse chestnut/buckeye) - so glossy and rich
The shade of red of Christina Hendricks’ hair
Tiny babies’ hands and feet - especially tiny little nails
Old weapons. I once saw an ancient Persian dagger for sale for a truly outrageous price, and almost bought it just because it was so damn gorgeous.
Crumbling lighthouses. Abandoned Victorian buildings. Ruins of any kind, really.
Mikael Åkerfeldt’s (lead singer of Opeth) voice.
Snakes. The way their scales fit together, their eyes, the way their cute little tongues flick out…not as cute as cats, maybe, but more beautiful.
The crumbling stone steps made during the 1930’s depression, and the trails that you find in an old public park. I was walking on a new wooden walkway through the zoo, and looking down the hillside below were the remnants of those old steps seen through the weeds and bushes. They looked like the remains of a lost civilization.
Cemetaries are beautiful. The older, the better, though - I saw a crumbling old monument listing to the side, in a little plot not a mile from my house, date of birth 1778! (endless rows of flat stones set in the ground, efficient, but not beautiful).
Van Gough’s Starry Night in person. Literally, I cried.
The Sandhills in Nebraska
Same here. Also 2-3 suspensions, particularly with minor seconds.
(Forgive me, I haven’t read the whole thread!)
Laughter.
I find it beautiful whenever I see it. Even overhearing others having a gigglefest, or a loud hearty laugh. Or unexpectedly making a child laugh! Or your Granny. Laughter is awesome, like it’s own little miracle. Maybe you’re walking through your daily life, unfolding as usual, and find yourself on a street corner, and witness, with those around you something that causes you each to laugh out loud. That’s an awesome moment, that laughter is like an inoculation that bodes a good day, as life continues to unfold as usual, for those observers. Laughter is like elixir or quicksilver. You can’t hold it, seems to have a life of it’s own, is just so wildly random and unpredictably awesome. Fills you up, then slips away.
Caribbean blues, teals, especially in beach glass. I’m a huge sucker for it in the best “oooooOOOh shiny” tradition. 
Certainly a contender.
Perhaps it was lack of sleep, but I’d spent untold hours struggling to come up with a shortest-path algorithm at all, let alone one that would complete before the Universe ended in Heat Death. I remember the experience of reading and understanding Dijkstra’s algorithm as a glimpse of something very, very beautiful.
When I burn the roof of my mouth on hot pizza and have a little skin tag I can twirl around with my tongue.
As we are not supposed to be posting things that are universally considered beautyful(sunsets etc) in the spirit of the thread my offerings are bomb or napalm runs when viewed from the air, big storms on coasts, steam trains in action and old libraries.