The last items are always babies of the characters, right? And no, I'd be unlikely to buy that new/full price. Used/discounted is another story, although they'd have to be darn cute.
As for goofy licensed stuff, I found packs of tissues at The Dollar Store a while ago, so that's already been taken. And there was the Crazy Foam bath soap, and the Good 2 Grow "suck the brains out of a pony" drink toppers, and plates and bowls, and mugs.... So what else could be left to slap a pony on? How about something like shoelaces, something in the style of the now old M6 lanyards? I'd buy those if they were long enough for my shoes (and rainbow colored too, please!)
For the last brand new item I will buy, and pay full price, will be Kotobukiya Rarity. It will consume the pony budget, new and used, for quite some time.