Both team and individual accomplishments need to be vitally recognized.

Contests and rewards are great. But have you recognized things on an individual level? Your sales manager maybe would like some PTO to do volunteer work while your star sales agent is really passionate about a hobby (which you demonstrate by say, giving them an appropriate gift card after a particularly big sale.)

Fostering companionship over competition can go a long way as well so you don't have people feeling bubbling resentment over that one goldmine territory/client/etc. This is why your employees still need to be rewarded on team efforts when times are good-- so there's no impression of playing favorites.

Balance is key.