I had quite a few ponies when I was a child. My first Pony was Cotton Candy (hello! it's pink! it's a pony! what's not to like?) followed closely by Blossom, then Seashell, Bowtie, Applejack, Glory, Firefly, etc, etc. I had quite a few playsets, too. Being an only child can make for some good Christmases, even in a single parent family.
Because I'm an idiot I gave up my childhood ponies when I was 14. I could've kicked myself about ten minutes later, but it was too late by then. I really wished I'd kept at least a few of my favourites. My only consolation is that I didn't have any really rare ponies in my childhood collection. I'd always really wanted a Mimic, I thought she was so pretty. But I only saw her in stores once, and I chose to get a newborn twins set instead.
My favourite childhood pony was Sunbeam. I got her relatively late in my childhood, when an older friend grew tired of ponies. She was in pretty bad shape. She had no tail, and her NDS was covered in bright pink marks. Apparently she'd been left in a plastic bag in the sun one day. Probably because she was in such bad shape I made a point of playing with her so she wouldn't "feel left out" and she became one of the main ponies in my herd. I wish I still had her. I hope she was found by a customizer and turned into something beautiful and didn't just end up in the trash.
My adulthood collection surpasses my childhood one in quality and quantity. I've been lucky in the last few years to get some grails (including the complete set of Big Brothers with hats, bandanas, and combs thanks to Rosesare's raffle on the Arena and three baby TAFs thanks to my closest friends). But they don't quite replace those childhood ponies with which I built so many memories. I get nostalgic when I look at my pristine Sunbeam for that sad little half-pink bait pony.