I guess by "toy" we have to limit this to stuff owned below the age of 18, otherwise recently-acquired musical instruments will take the thread over!
My Topper dinghy, probably, although I'm not sure I'd call it a toy. My folks sold it when I left home, which was OK by me - I was a bit too big for it by then anyway, and I didn't have anywhere to sail.
Also my collection of Warhammer figures - metal fantasy and SF figures. I loved building and painting them. Creativity-wise, guitar replaced those at the age of 19 though, so they sat in the loft at my folks' place for years, then in our loft for some more years. I finally sold them to a kid nearby for not very much money at all - I could have got much more for them on eBay, but I thought I'd rather sell them to someone who'd get some real enjoyment out of them. When I started digging everything out of the boxes, the lad actually lost the power of speech for about a minute, he was so overwhelmed with how much stuff there was! :-)