My fave key chain tool is the Leatherman PS4.  The pliers are tiny, but effective.  Even smaller is the SAK Classic - blade, tweezers, scissors.  Variant models sport either a ball point pen or a small light.  I have found both useful.  It ain't no multitool, less you can grab and pinch somethin" with it.
Usual disclaimers....
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Geezer in Chief