What are these suffixes used after the call sign?
Heavy - all aircraft with maximum take-off weight greater than 300,000lbs (whether or not they're operating at that weight) It's to highlight to the controller that wake turbulence could be a problem for a following aircraft.

Super - Airbus A380: As for 'Heavy', but more so.

Flight of X - All the rest relate to groups or formations containing that number of aircraft.

These originate in the FAA regulations and are summarised on Wikipedia

There are a number of other unusual suffixes including 'Concorde' (used only by British Airways for the now retired Concorde), Lifeguard (for medical flights), and others