I've never needed my handheld radio in flight, but the planes I'm renting only have a single radio so I like having a backup.
I also carry a pair of eyeglasses in case I have a problem with my contacts, but so far I've never needed them.
A firearm is another piece of gear I haven't needed to use (yet), but I don't clutter the flight bag with it. Instead, the .38 snub is in a pants pocket, the 9mm is carried IWB, the .32ACP is in an ankle holster, the NAA .22WMR is in my hat, and if I'm flying over a remote area there's a S&W .357 in a shoulder holster. Unfortunately, this does cut down the fuel load in the Tecnam LSA, but it's better to be safe.