I just got my blackberry yesterday. I logged into facebook, and everything was synced automatically, including my contacts and calendars.
Hit up your contacts from Gmail, or head to google.com/contacts,
and hit the "Find duplicates" button in the lower-right area.
You'll be provided with the list of contacts with at least 2 entries each,
which you can view in expanded form, and then either merge together or kill off.
Not that this is some new-fangled tool or an advanced feature,
but I know at least a few Google users' primary annoyances with contacts can be salved,
if not cured, with this little button.
Ahmed provided by (Kevin Purdy) from (LifeHacker)