For me, it depends on how I’m using the ATV/UTV. I keep First Aid kits and basic toolkits stashed in everything I own with wheels and an engine. For my ranch UTV and minitrucks, there’s usually a length of barbed wire and stretchers, pliers, etc. For my hunting Ranger and ATV’s, it depends how and where I’m hunting. If I’m driving to my hunt in or on it, I usually have a block & tackle and gambrel, spare batteries and a spotlight, in case I need to track after dark.
I’ve hunted where my UTV was the means to access the spike camp, so I kept a lot more on the UTV for that, in terms of supplies, especially emergency stuff. For my normal whitetail and coyote hunts in KS, the ATV is just a low impact, high speed means of crossing ground, so in an emergency situation, if I can make it to the ATV, I’m only minutes out to my truck.