Leavings mainly...
Tenants in my old home - lot 1 left a garden full of dog shit and I mean full, there wasn't a single spot you could stand in without standing on a turd, and most of the turds were mouldy. The only places not covered in shit had plastic kids toys on them... how their poor children had ever used the garden I don't know. I don't know how the dog (the dog they didn't have according to the tenancy agreement!) managed to go out without standing in it.
Loads of bags of crap in the house - a mix of obvious stuff and also household rubbish.
A big floaty turd in the toilet.
I had to go sort it out - messaged ex tenant for nearly a fortnight then she vanished completely (blocked me!) without making arrangements to collect her stuff (or paying any further rent and she owed me 2 months at that point).
Funnily enough despite being uncontactable, as soon as we started putting black bags of stuff out ready to load up to go to the tip, she appeared.
Came storming out of the new boyfriends twat-mobile (loud exhausts, blacked out windows), screaming and swearing that I was stealing her stuff. I said she was free to take it, but she'd been given 2 weeks notice to collect. She loaded up, and sat in her car rummaging... then they drove off, emptying black bags of rubbish out of the windows all the way up the street!
Lot 2 took MY washing machine, but did at least leave the garden ok and the toilet turdless.
The buyer when I sold... claimed I had left the out-shed full of rubbish!
The cheeky bastards had used it to dump a load of rubbish from another property they'd bought.
A combination of my dated photos on leaving plus a friend getting pics of post/paperwork/notable knackered fittings from the black bags with the address of the other property - which had been sold to them by the same estate agents I'd used, sorted that one out!
Even the EA was astonished at that, the effort required to bring it from property one, dump it at property 2... they can't have had the right licences to dump at the tip.