Low ceilings, tiny windows, a lack of natural light.
In the shadow of huge trees that I did not have the right to remove, or were on my land but too close to the house.
A badly extended, bitty, rabbit warren-like layout that didn't flow well.
Very narrow/steep staircases and narrow, dark corridors
A bus stop or traffic lights outside.
Shared access/parking
No off street parking (although I realise that that is something that is not always possible depending on your budget and location.)
Somewhere where there was nowhere to park at all immediately outside the house.
One loo, unless it was a 'two-up two-down' house or a flat.
I would not discount it altogether but I would think very, very carefully about anywhere opposite a public open space, an alleyway or a green, a play area or backing onto a recreation ground or park. It would really depend on the area and the distance from the house, but it has the potential to be disastrous. I went to look at a really great ground floor flat in the heart of a lovely small city but the master bedroom window opened directly onto a grassy area by the riverside path and it was obviously the local hangout for drunks, dossers and druggies. It was bad enough in the daytime so God knows what it was like at night! I am lucky they were there causing a nuisance when I viewed otherwise I might never have twigged.
On a really busy road unless it was set very well back, and even then I'd think long and hard about it. I've been in houses that literally shake and rattle every time a fast car or a big lorry goes past within 6 feet of the front door.
A kitchen that was open plan to the main/only living area
(I don't mind a kitchen being open plan to a casual family area so long as there is another more formal room where I can close a door.)
Likewise unless the house was very small I would not want the only dining area to be totally open and in full view of the kitchen. All this 'chat to your friends while you cook for them' is overrated nonsense - no-one wants people under their feet while they are cooking and no-one wants to come for dinner and sit surrounded by your washing up, or to have to shout over the sound of you clattering around and frying stuff, while they chat between courses. I like an informal eating area in a kitchen as well as a separate dining room/area though, budget permitting.
Would not ever again take on a huge, very overgrown garden. It's so soul destroying to try to get on top of it.
Spiral staircases, unless it's a second staircase and all or most rooms can be accessed via a normal one.
One of those really nasty cheap conservatories that is entirely made of plastic, with shiny plastic panels instead of brick walls at the base, and a plastic corrugated roof.
Thin walls and poor sound insulation in flats and modern terraced or semi detached houses.
Any of these new builds that claim to have four bedrooms and three en-suites when the bedrooms are so titchy there's no room for proper wardrobes or decent sized beds, and the en-suites have no windows and require you to be Houdini.