I like a good guestbook with lots of local recommendations from the previous guests as to what is good and what is not good!
Not essential but would always make me want to return, would be a good welcome basket - butter, milk, tea, coffee, bread, jam and wine
For a beachy place some basic beach stuff - buckets, spades, boogie boards, fishing nets.
BBQ and BBQ equipment.
A really good set of sharp knives (although I often take my own these days) and good coffee maker or cafetiere.
A stash of cleaning stuff and bin liners - including good cleaning sponges in clearly marked floor cloth, bathroom sponge, kitchen cloth.
Clothes airer to hang beach towels, costumes on after a day at the beach.
A DVD player and some DVD's (the ones from the sunday mags are fine) it is nice to sit down and watch something you wouldn't necessarily have chosen yourself!
Books/magazines.
Local leaflets/maps.