I carry my cell phone though I'm often out of service range. I carry a tube, CO2 (2), small inflator tool, a tire boot, a few dollars, 3-5mm allen wrenches. That's it. What else would I need? Bandaids? Nah. Sometimes on really long hot rides I'll carry a small packet of chamois cream or sunscreen though I usually just go with 40 or 50 spf at the start and it's good enough.