Strobe, spare VHF (zip lock bagged), survival blanket,
(the tin foil looking thing), 1 small bottle water, 1 nutrition bar, sat phone (zip lock bagged) when I have one (I rent one when I'm off alone for a while - keeps the family from whining too much), spare gps (also zip lock bagged).
I'm not headed way offshore at this point, so things could/should change . . .
This goes in a smallish backpack that I keep at the companionway with my inflatable pfd/harness (when I'm not wearing it).
Would love suggestions for more, but it's gotta stay small and pretty light.