Cardiff RFC | Oxford University RFC | Newport RFC | Swansea RFC | Llanelli RFC | Pontypridd RFC | Glasgow Academicals RFC | UCD | Pontypool RFC | London Welsh RFC | St. Peters RFC | St. George’s Hospital Medical School RFC | Hawick RFC | Aberavon RFC | South Wales Police RFC | Neath RFC | Bedwas RFC | Penarth RFC | Medicals RFC | Watsonians RFC | Vienna Celtic RFC | Tylorstown RFC | St. George's Hospital Medical School RFC | Southend RFC | Shannon RFC | Selkirk RFC | San Francisco Golden Gate RFC | RFC Liège | Percy Park RFC | Old Illtydians RFC |
In 2004, Gannon captained the Ireland Under 21 in the Under 21 Rugby World Championship side while playing for UCD.