Regular everyday riding, I don't carry anything other than a cell phone and a Road ID. When touring, I carry a generic store bought first aid kit. I passed a guy today with a nasty cut on his leg/knee. He didn't have a first aid kit, nor did I.
Last year, I went down in the rain. Landed on my face. A couple of minor cuts and scrapes, thought I lost a tooth and a gash inside my mouth. Washed my face with rain and my jersey, called my wife to keep her on standby and rode home.