1.
When Tony was 4, Howard and Maria set up a playdate with the son of the billionaire Brian Xavier. Charles was a nice kid, smart, if a bit arrogant. He hadn't many any other friends, so Mrs. Xavier called on the Starks, who took him to the Xavier Mansion, where Tony was presented with his own pony, a gift for coming to play.
Three hours, a call to Jarvis, and a broken arm later, Tony decided horses were the worst creatures on God's green Earth, Charles didn't care about anyone's feelings but his own, and he never wanted anything as horrid as a to even resemble a pet again.
He left the pony.
2.
When Tony was 7, his occasionally visiting "Aunt Peggy" presented him with a first-edition copy of War of the Worlds.
Tony tried to invent his own version of a Martian, hoping to show his dad his true potential as an inventor.
He presented the idea to Howard, who laughed and patted him on the head like a silly little kid, commenting that Cap had fought actual alien-like creatures.
He threw the book in the bin.
3.
When Tony was 10, Emma Frost, a daughter of his mother's socialite group, invited him to her birthday party, where everyone was given a piece of diamond jewellery.
Tony used his cufflinks to reinforce a saw in order to test the extent of Emma's diamond form. When a piece of her hair easily cracked off, they both became terrified and Tony called Jarvis to take him home.
He destroyed the saw and gave Emma back the diamonds.
4.
When Tony was 12, his father, in order to impress investors and the press, rented out a zoo for Tony's birthday.
He invited all his business associates' children, who were more interested in their private tour of the zoo and open-petting policy many sections of the zoo adopted than touring with or even speaking to Tony.
Tony, who realized he still didn't care for horses or most other of the four-legged animals, spent the day in the aviary, watching the various birds and wishing he too could fly away.
He stowed away home in his Aunt Peggy's car with no one the wiser until later that night.
5.
When Tony was 16, his father bought him a car.
He didn't have a license, but his new friend and roommate Rhodey offered to drive him where he needed to go until he came of age. Most of the students at his new university mocked Tony for his age, his size, and his brains. Rhodey told him to get in the car and they drove and drove and drove for hours. They ended up at a concert for a band called Black Sabbath, and all the noise in Tony's overwhelmed head finally stopped with the music he was hearing.
He gifted Rhodey the car.
+1.
When Tony turned 18, his friend Rhodey looked around at all the expensive gifts the billionaire heir was receiving.
He swallowed, taking in the boats, the money, the cars, the deeds to various beach houses and ski lodges, and the luxuries he could never afford to give his friend.
He turned to leave, but Tony caught his eye, abandoning the posse he'd recently acquired and running over to Rhodey. Rhodey quickly offered the only gift he could afford with his financial aid, and looked toward the sky, embarrassed.
Tony tore open the small package while all the people around him gawped and giggled at the humble offering, before Tony cut them off with a glare, before pulling Rhodey in for a long, grateful hug.
He kept the band t-shirts.
A/N: Tony Stark Bingo Fill: Writing Format Five Things. Title from Black Sabbath's Iron Man.
I'm aware the T-shirt Tony wears in Avengers is from the 1978 tour, but he would have been too young to attend, so let's just assume this is what started his love of graphic tees. We'll also assume Charles and Emma were dealing with their own problems, as their parents tried to set up their playmates as well. I also claim no knowledge of diamonds nor diamond saws.