Everyone has something that they've got loads of already but can't resist a new addition to the collection.
For me it's coats. I have five Gilets, and probably eight jackets and several winter coats, I added to the collection yesterday with a lovely Mint Velvet Boucle coat. God knows why, just loved it!
I'm also partial to mascara, lip gloss and trainers. It's actually an illness , right? 
What's your thing ?