Essentials would be a washing machine, dishwasher, TV and DVD and/or video, proper shower (can be over the bath), somewhere to sit out, parking at the property or safe on road parking near the cottage (not a car park pass for somewhere miles away)
Decent sharp kitchen knife - nothing fancy just something capable of slicing tomatoes or cutting up potatoes. It got to the point a few years ago where I bought one to take on holiday as they were always so terrible but I think I ended up leaving it somewhere.
Decent pillows - one flat pathetic offering each is not enough!
DH wants WiFi these days but frankly, I think he would have a better holiday without it.
Buckets and spades to borrow.
Boring but necessary stuff like bin bags, washing up liquid/dishwasher tablets, pepper and salt, decent iron and hoover.
If they want you to leave the place clean and tidy a decent range of cleaning materials is useful - sometimes they leave nothing but a bucket and a j-cloth.
Leaflets from the tourist information of attractions in the area - highlight of my first evening is working my way through and working out what we are going to do.
No velour furniture, nursing home style chairs and old melamine kitchens either. Too depressing.
I'm very fussy though.