Wakfu Rewards

I don't recall a game that really rewarded it's player base for participating in betas.

Wakfu had a few interesting incentives for extra-curricular participation in the beta including:
- gear and titles for reporting bugs via a 10 point system
- a Wakfu haiku contest

As a freemium mmo, it also rewarded the people who bought subscriptions (very reasonable!) with more in-game gear, titles and perks.

Besides having the ability to reserve one name for the launch (the most important thing to me, imho), SquareEnix also gave this reward for participating in the beta:

Head over to the site for more information; basically if you loved Final Fantasy Tactics, you'll probably like Wakfu as well!