A few (crappy) ideas are:

 - **Optimist** - Has made at least 150 votes and none are downvotes

 - **Street-cleaner** - Has at least 10 flags and less than 20 votes

 - **Socially accepted** - Has 5 accepted answers in a row.

Edit: added: 

- **Pessimist** - Has made at least 150 votes and over half are downvotes