Some more connectors...
  Banana plug used in amplifier connections, test equipment, sanalogue synthesizers. Robust connection, stackable, handles high amount of current.  Assumes ground connected in another fashion - may be paired for signal and ground configurations.
Typical 1/4" phone plug with Tip Sleeve Ring patch bay plug  (right) used in connecting devices in a patch bay.  Tip and sleeve carry balanced high and low signal, sleeve is ground.