Ooh, I've got a niche but life-buggering one.
I've yet to be able to find a powerchair with an ignition key. If you want an ignition key, you have to buy a mobility scooter with a tiller in front, meaning the wheelbase is half as long again and it's a fecking nightmare to manoeuvre on buses and tight little shops.
I can see no reason for this other than an attempt to enforce some sort of disability coding solely for the benefit of passers by:
scooter = could walk but can't be arsed;
powerchair = can't stand at all.
If like me you can stand up and walk a few metres, you're stuffed. I want to be able to take the bus into town to my optician's, which is in an older building with steps in front and pokey rooms. I want to be able to leave my conveyance secured outside, go up two steps, walk ten paces and sit down.
If I use a scooter, it's hell on the bus (10 point turns amid the shopping bags and impatient passengers); if I use a powerchair which can turn on a sixpence, any passing scally can ride off in it while it's abandoned outside. (Yes, this does happen, see MN passim. )
I have now managed to find a powerchair that still doesn't have an ignition key but can be programmed to be locked by some complicated sequence of joystick movements and on/off button presses. It takes me 3 or 4 attempts to work a phone correctly once I'm tired: there's no way I'm going to be able to operate that. Just USE AN IGNITION KEY.
There's a reason vehicle ignition keys were invented decades ago, and that reason hasn't hasn't changed.
And breathe...