 Born in Vestmannaeyjar, Iceland, Gunnar started his career at Íþróttabandalag Vestmannaeyja.After establishing himself as the best striker in the Icelandic Premier League, he was transferred to Halmstads BK in Sweden in 2004.Here, he only narrowly missed out on the league title in his first year and won the Swedish golden boot in the following season (with 16 goals).