What I would consider the usual: Kind, honest, trustworthy, no drug issues, loyal.
Beyond that (non-frivoulous):
Funny.
Has to be a fully-functioning grown up (e.g. no pile of debt for no reason, doesn't let his insurance/passport/drivers license expire because 'no one reminded him' to renew them etc.) If I wanted someone I had to look after, I'd give birth to them.
Ambition. I don't require that he have a white-collar career, but he actually has to treat whatever he does as a career. If you're a bricklayer, you'd better be aspiring to be the best damn bricklayer in the city, or have plans to own your own bricklaying business, or something.
No over-attachments to exes. This also continues to: no weird issues that surface regularly because of an ex. After a certain age, we all have baggage. I expect that someone who has determined they are ready to be dating will have dealt with theirs and it will be stowed neatly in the overhead compartment.
Has couth/is not cheap/is comfortable in relatively upscale social situations. This is necessary because of my career, and since I don't plan on changing careers soon, I need a partner who will be good in these situations too.
Understands family obligations. This one is big for me, as I'm an only child, so when my parents become ill/infirm I can't just assume a sibling will help with their care while I live footloose and fancy free halfway across the globe, or something. I'm not saying that I'd want them living with me, and they're well enough off, so I won't have to look after them in that sense, but I would not be comfortable leaving them parked in a nursing home while I visited once or twice a year.
Gets along well with the majority of my friends/family.
Possibly frivolous:
I recently had a fantastic date with a guy who was very hairy. I'm not sure why I was surprised, given that he told me he ethnic background before the date, but I still found it off-putting that I noticed ear hair. He's in his 30s, was very well-dressed, and well-groomed, works in a profession where appearances matter, so I was just surprised at that. Wondering if I can say, hey buddy, I wax my nether regions, you have to wax your ears (and possibly back/shoulders if they turn out to be as hairy as I expect that they will) if things go that far.