Age: 39 years, 1 month
Place of Birth: Dublin
Height: 5' 8"
Gary played youths football at Tolka Rovers before signing his first professional contract at Bohemians in 2000. He made his league debut against Shamrock Rovers on the 14th August and spent three years at Dalymount Park without ever establishing himself as a first choice striker.
In 2003 Gary signed for Waterford United and did well for the Blues before suddenly quitting the club for unspecified reasons. He returned to league football in 2004, spearheading the Dublin City attack in a dramatic season that culminated in relegation from the Premier Division. Gary scored eight league goals and was nominated for the 2004 PFAI Player of the Year award.
In December 2004 Gary joined Shelbourne and made his Shels league debut against UCD in March 2005. He netted seven times in 18 appearances in 2005. The following year Gary scored ten goals in 30 appearances and won his first career medal as Shels won the 2006 league title.
On January 3rd, 2007 Gary left the now financially troubled club and moved across the city to join St Patrick's Athletic where he spent two seasons before signing for Sporting Fingal in January 2009.
Fingal gained promotion from the First Division that year and also won the FAI Cup, beating Sligo Rovers 2-1 in the final at Tallaght Stadium with O'Neill scoring the winning goal. In 2010 he scored a further twelve goals for the Ravens and was due to play for them in 2011 until the club folded in February.
In February 2011 Gary signed for Shamrock Rovers and made 39 league appearances over his two seasons at the club. But 2012 was a disappointing year for Gary, who made just 8 league starts, and in November 2012 he signed for Mick Cooke at Drogheda United. 2013 would prove to be a turbulent season for the popular striker. He scored four times in 16 league games and scored in Drogheda's Setanta Cup final defeat to his old club Shamrock Rovers. He also played in both legs of Drogheda's Europa League tie against Malmo FF but his season was cut short when he was diagnosed with testicular cancer in September. He took no further part in the season but recovered sufficiently to take up a player/coach role with Drogheda ahead of the 2014 season.
Despite the title of play/coach, Gary was still a key part of the Drogheda United line-up in 2014 and went on to score six goals in 29 league appearances as the Drogs finished ninth in the Premier Division. It would prove to be Gary's last hurrah for Drogheda and he left the club in January 2015 to sign for Tolka Rovers.