I like OP's paint can opener; I have a small flat-bladed screwdriver with the edges rounded so they're not sharp. Also carry a valve core remover, small bottle of sealant and a frame pump. CO2 is not reliable enough for me.
And I also have a spare pre-glued tub as well (which reminds me I have to do my annual glue refresh since I've only used it once) and even have a bag for two tubs on longer rides in areas where phone coverage is iffy - call it belt, suspenders, and extra set of suspenders
