I guess I'm pretty lucky. I generally save up for stuff I want out of the funds we have for, for want of a better word, pocket-money. When there's been something I really want/need/bother her about for long enough, then I can dip into the savings.
Mind you, she knows of my OCD-type repayment plans that I have in my head in order to repay those savings...
In all honesty though, most of my new stuff is paid through the sale of my old stuff!