real estate agents need to practice and master their abiity to LISTEN..... the most important skill....listening....

Determination. If you think it is easy you will be wrong but if you work hard and stick with it and learn as much as you can you will be successful.

Ability to focus...on integrity, listening, work, character, and whatever...Focus lost is  goal lost.

Honor.   As in, your word is your bond.  You live by the Golden Rule. 

Let's start with honesty.  Without honesty you won't go far in this career or any other.

Good luck with your article Cody Carmen 

Cody,

Someone who likes people and knows how to engage them in a conversation without it being all about ME, MYSELF, and I.  They also should be a good listener. A

Bounce-back-ability!  (and learning to bite your tongue)

That they understand that the one trait is that they recognize there are many traits that are important.

I don't think that there is ONE essential.

I have seen plenty of successful agents who are missing all of the traits below, even some here on AR.

It takes a combination of skills and qualities.

Honesty.

Tenacity, ability to listen, ability to deal with rejection. Guess that's three!

Many great answers here...I'll pick Barbara Todaro 's response if I'm only allowed one!

Cody Carmen - again - just one? I'd say good habits. Discipline. (Oh that's two....)

Good listening skills

They need to learn to listen.

A never give up attitude.

Optimism is helpful too in addition to all the other qualities listed here

Being able to listen

Cody Carmen Integrity!

Focus and preparation.  

I'd say PASSION.  With passion you are willing to do, and learn, all the things that are necessary to be successful.  

Perseverance...!

IMO - Patience

Determination.

Patience

There are many good answers here and I agree with Bob Crane it takes the right mix to succeed. One trait not mentioned that is critical is persistence.

If I have to choose just one, I would say you must be passionate about what you do because, if you are passionate you will do your best in all areas because you want to succeed. And if you are passionate and giving 110%, it will flow over into the other areas of honesty, integrity, listening skills, communication, etc.

Integrity

Determination to complete tasks & stay on track in a timely manner.

Communication skills

Cody, 

A short memory.  What just happened, good, bad indifferent has to be forgotten and moved on from.  

Thick skin.. because you have to learn how to handle alot of rejection and you have to learn how to self motivate and get up when your down.

For me it would be caring about people, because it shows when you are a happy person, and when that 'smile goes up to your eyes' everyone sees it and feels it.  I think if one cares, they are willing to do more than what is required, and we all want a real estate experience to go smoothly, because there can be challenges on both sides.  And if you care about people, you are willing to have more patience with difficult clients (not to be confused with 'the client from hell' - HA!).  Also, caring for me, means that I can have the same satisfaction and happiness for a client, who is either a Buyer or a Seller, because they are fulfilling their dream and going on with their life.  Best of Luck Cody Carmen, with your new article!!

Good listening skills.

Positive and joyfull attitude.

Should work long hours

persistance

Responding to ALL leads no matter how wacky or how small because an agent never knows who these people might know and might refer you to. 

The ability to network.

Consistency.  In skills.  In effort.  In achievement.  

Barbara Todaro summed it up well. Listening tops the list followed by the ability to ask the right questions and then, Listen!

I would have to say honesty.

You gotta like your fellow man and not just in words but in deeds

returning phone calls in a timely manner

I agree with Mary Yonkers that honesty is very important, self disicpline also helps.

Different agents have different traits in order to be successful.