Which trait do you value the most in a co-worker?

I disagree: humility is the opposite of arrogance. The ability to accept that you don't know something (and are willing to find out if necessary) or that your own 'facts' may not in fact be true is career enhancing. Arrogance can be useful (e.g. Steve Jobs) but usually it leads to team dysfunction and staying committed to unproductive paths.

Humble does not mean 'meek'.

Remember, friends help you move. REAL friends help you move bodies.

I have been at the same job for 39 years my main reason for staying is variety, along the way there have been some interesting people 

1 was into amateur radio, another was in a band, another repairing/modifying cars, I sometimes fix vintage computers,

and the office lady that would organize an outdoor event occasionally, no one bought up sport or religion best group ever, 

I would like to include Trust on the list.

I trust that when you say you will do something, you will do it. Trust me when I tell you, If I am going to stab you in he back. You will know, I am the one doing it and when it will be done.

When hiring people I first make sure they are competent and able to do the job.

If I have multiple candidates who meet the basic capabilities I then base my decision on attitude.

I want people who will work with minimum supervision and who will do a good job.

I never hired anyone who had to be constantly pushed to do the job they were hired to do.

I never hired superstars with an attitude. They are too difficult to integrate with a team.

It is far easier to take a team of good people and make good software than it is to live and die on the capabilities of a cowboy.

Good points. Perhaps enthusiasm needs to be more narrowly defined to be enthusiasm to get the job done properly.

Jan Cumps said:

It's one that may slow you down in your carreer growth.

I'd say it's more likely to slow them down.

For you, a humble co-worker can offer some stability to the team as you aren't having to replace them every few months as they leave the team to move up the career ladder, leaving your team short as you wait from them to be replaced and to get up to speed.

Also for you if you have humble co-workers, it's you that is likely to progress up the career ladder as you are more likely to be seen as having the 'leadership qualities' and not them.

I don't think I could pick any one trait in isolation as it's going to be highly dependent upon what it is that you are working together on and how the traits of co-workers interact with your own and others in the team.

Sometimes creativity and over enthusiasm where it is not needed can just end up with a big mess that takes you longer to undo and redo than if you did it yourself slowly and methodically. Or it can result in a lot of wasted effort and time because something has ended up far more complicated/aesthetic  than the objective ever called for. Other times it can take the project to new levels or even take a failing project over the finish line.

I've worked with miserable unenthusiastic people many a time but under all the muttering and grumbling they are methodical, pay attention to detail and don't get easily distracted. Then I've worked with the hyper enthusiastic individual who has to make a theatrical performance out of everything (and has to check their mobile device every 30 seconds just in case the world has ended and they don't want to be the last to have found out) rather than concentrating on focusing on the task in hand.

Experience is sometimes needed, other times it is just more of a willingness to learn that is required. I often wish some of the more experienced co-workers would refer to the documentation (and create documentation) rather than waltzing in and assuming it is the same as what they have worked with before. Other times their experience is invaluable, but we perhaps hope that is why they were hired for the job/selected for the project.

Coordination is often essential - ever tried to assemble something as a team where the other person just can't seem to coordinate with the activity ?

I'm not convinced that Humbleness is a great trait for a worker. It's one that may slow you down in your carreer growth.

Good point. Dependability is right up there.

I like your big 3 short list. The tough bit is choosing which is the most desirable.

For me, integrity is a must have, go / no go criterion, but if that is a given then enthusiasm is probably next.