There should be system to send users gifts like free stickers
103435
May we have some more SO stickers, please?
53582
More than one person should be able to offer a bounty for the same question at the same time
8875
How to implement a reputation based system with badges in Drupal similar to StackExchange sites?
156734
Mechanism to provide feedback to reviewers who rubber stamp?
148762
Share buttons for chat events!
45965
Should the user be forced to sign in for a wish list on an ecommerce site?
85843
Reminding new users of accept/upvote "duty"?
38479
A note making feature in the personal page
113416
Allow users to put their e-mail in posts?
74901
Provide a non-derogatory message for self-requested suspensions
10461
How to distinguish gift from payment for the service?
82827
Giving cards away in Catan
117247
Implement friendly URL for badges
23644
A "friends list" on Stack Overflow would be nice
136340
Popular alternatives to "thank you"
52653
How can I PM people on this site?
17742
Encouraging users to create an account (and keep it)