How to uninstall the Service links module?
As far as I can see, Service Links 7.x-2.1 does not create tables of its own and the uninstall hook only deletes some configuration variables. 

If you can't see the module in the uninstall tabs then you have probably deleted the module's folder before uninstalling. If this is the case, you can restore the module's folder and then uninstall the module (no need to enable it again). 

Or you can run DELETE FROM variable WHERE name LIKE 'service_links_%' to your database.