Places advertised for rent that don't make it clear in the advert that they won't accept cats, or dogs, or smokers.
Property search websites (PSWs) that don't let you restrict your searches for places that *do* allow dogs, cats and smokers.
Agents that call you while en route to the first viewing in ages of a place that allows cats, dogs and smoking; to tell you the property has been let, when the only reason you weren't able to get a viewing earlier than the people who took it is 'cos the agent couldn't be arsed to work after 5pm that day.
PSWs that have search tools that don't let you say "detached + (house or cottage)"
Agents that crop the picture of the property to avoid showing the dogmeat canning factory just next door.
Agents who despatch the part-timer to be your guide for a viewing. "Dunno", "I only work Sat'dy"...
Landlords who stipulate "No children, one dog allowed, one cat considered" in their adverts. If I have no children but do have two cats, is that better or worse?
"150' long garden" - but only 2' wide.
Agents who don't listen to your requirements, and spam you with crap. No, I don't want a terraced 1 bedroom flat in Mayfair for half a million quid, nor do I want a derelict hovel in Leeds for tuppence.
Agents who don't remove properties that they've already let/sold from the bazillions of composite websites they've put them on.
The fact that *none* of the buggers have got RSS feeds of their new properties.