The grating over Vash's heart was put there after he nearly died by being shot in the chest (for the third time). A doctor suggested it because it would stop most bullets.
Vash chose his own name, so did Knives (Vash the Stampede and Millions Knives)
Vash spends a lot of time wishing he'd been an only child.
Unlike Ed, Vash takes very good care of his prosthetic arm. That and his revolver are cleaned every evening.
Vash can read five languages (English, French, Japanese, German, Italian) but can't speak any of them very well. Plus his German and Italian ar really rusty, he had a lot more use for the other three over the years.
Though we call him a PLANT for the sake of simplicity, he's not exactly, and Vash doesn't know exactly what he is either.
Vash actually covers up his body to save other people embarrassment more than himself. It's not the kind of thing people like to see =\
Vash is, technically speaking, a super genius. He learned to walk and talk and be an acceptable member of society in a year, and possessed greater empathy by the time he was one than most people reach in a lifetime. He's a faster reader than Knives but Knives was the smarter one. But chances are he could reprogram advanced technology if he wanted to.
That said, Vash is a jack of all trades and only a master a gunmanning. He always seeks out other people for any kind of trade skill. His boots, coat, guns, arms and pretty much anything else he keeps with him are custom made for him by the best of the best.
Vash has a rose, a kitty hat, a stuffed cat and a rain stick. Though they weren't all meant as gifts, he treats everything left with him as a gift. However, he doesn't like to keep things for himself so if someone else wanted any of these things, Vash would give them away freely.
Vash still has the rose he got from Umeda. He keeps meaning to let it die naturally, but every time it starts to wilt he gets weak and pokes it with his energy until it revives again. Of all the things he's received at camp, that's what he's most attached to, and would hesitate the most before giving it to someone.
Speaking of red flowers, if Vash ever finds geraniums the entire Chapel will be surrounded by them in a month. In a perfect world, Vash would only use his super mega PLANT powers to make flowers grow.
Vash doesn't protect the zombies or the wildlife, but he doesn't kill them himself.
It takes roughly two shots of his Angel Arm to make Vash's hair start to change. Doing the math, he can shoot it three times being using up his life.
Vash was born roughly around the year 2407. He's now (again, roughly) 150, making his time 2560-ish AD.
Both times Vash has used his Angel Arm, his psychotic twin brother basically raped him into it. The first time resulted in the deaths of a hundred thousand people.
Vash can see ghosts and residues of the dead
Vash and Knives looked a lot more alike prior to Knives going completely bonkers.
Vash cannot cook but he's an expert at getting people to cook for him
Vash rolls off the bed while he's sleeping ALL THE TIME
Vash has hunted and killed his own food, he just doesn't like it =\
Wolfwood is not the first person to call Vash Tongari/Spikey
Vash really can't play chess, he isn't faking it. It's because he's never willing to lose any pieces.