What is something important to leave at your friends house, besides a purse, wallet.
That's weird. I've never ever heard of anybody cluttering their friend's house with their personal belongings. You don't 'need' to leave stuff at your friend's house. And leaving your wallet unattended is foolish- in this day and age people will screw over their friends in a heartbeat to make some money.
The only instance I have heard of was when my friend left her abusive husband and she kept a suitcase with several changes of clothes, shoes, a bunch of cash, toiletries, snacks, and a coat.
Phone? iPod touch? Diamond gold ruby emerald sapphire jewellery set?