Have you ever wondered how your work contributes to the company as a whole? Is this something you look for in a job description?
It would kind of stroke my ego in the right way hearing that my work would be an important contribution to your company.
On that note though, simply telling potential job applicants that their work will put them in the spotlight, or will get them recognition amongst their peers is always a nice little perk for our egos too. Then of course you'll always need to congratulate employee's on a job well done, or something similar. Those of us who write code for a living rarely get enough credit for the type of work we do.
Something else I like to see is the opportunity for advancement(job position, and salary typically). From your perspective I think that would attract better job applicants that are goal oriented, and are always trying to do a better job. From my perspective I will be motivated to do a better job for you, because I know I can be rewarded for trying harder.
If you've got a work-in-progress job posting, let's see it! it'll be easier to make suggestions on a provided example.