What are the symbols in front of each deviants nickname?

They are status symbols that represent the type of member that a particular deviant is:

User Accounts

~ Member
* Premium Member
= Official Beta Tester
` Former Administrators or Senior Member
° Alumni
! Banned or Deactivated/Closed Account

Administrators & Volunteers

+ General Administrators
¢ Creative Team
^ Community Volunteers
$ Core Administrators (deviantART Employees)
£ Officially run deviantART accounts

You can read more about the Administrative members on the About Page.

Other

# Groups

No longer used

© Policy Enforcement Team
% deviantART Prints Team
: Premium Content Staff (No Longer in Use)
@ Volunteer Message Network Team