Erm.. everything.
Riding ponies out without either an adult or an adult knowing where we were going or when we might be back.
Sometimes not wearing safety helmets whilst doing that.
(and those we had were shared around, didn't always fit, had been fallen off in loads).
Riding motorbikes and mopeds with little regard for safety, or the max. recommended number of persons on board (being the one sat on the mudflap was precarious!)... again out and about miles from home over the commons and no one knew where we were nor could they get hold of us til we reappeared.
Building rafts and playing in the beck (very fast running with deep pools and steep waterfalls), out of sight and hearing of an adults.
Lighting fires.
Half cooking things on said fires, then eating the half burnt half raw results.
Building epic cross country courses through the woods that far exceeded our ponies jumping ability, which they knew and solved by stopping and launching us over on our own...
Exploring caves, alone though we did tell someone where we were going and when we expected to be back (vital the day I managed to backfill the entrance hole behind me and my lamp died and i was trapped in the dark for an hour with my friend the other side being utterly and completely wet and useless!)..
Rock climbing.. ditto..
Wild swimming, mostly with adults but this was really only because the best places were not accessible for little legs and no car.
Left to sleep in the back of the car outside pubs/village halls/party hosts home whilst adults carried on drinking/partying.
Left home 'alone' with the neighbours listening in (ie, with a key ready to run round if they heard anything untoward, through an intercom we had set up, worked actually, mrs next door came running round one day when I woke up screaming because id opened my eyes to a spider on my face! Oh and mrs and mr next door were a judge and a grammar school head!)...
Allowed in pubs late if I kept my head down and stayed quiet, and therefore accidentally saw my first male stripper when I was 8 ...
Allowed to help wire up explosives, accidentally allowed to handle plastic explosives ('whats this funny dirty yellow plastacine daddy?'), allowed to push the 'bang button'... (its no where NEAR as easy to get explosives licences compared to the early 80s)
Climb trees, jump off stuff, drive the car round fields, drive the car up the track, drive the tractor up the track, sit in the front bucket of the digger whilst someone else drives it, steer the van whilst sitting on an adults knee (minor roads)...
Sat alone on a single seat ski lift in Bulgaria, just a chain and being told to SIT STILL stopping me dropping many feet to my certain demise..
There are more, ive probably blanked them out, it is a pretty epic miracle I am not dead and survived into adulthood really!