Family and friends of the self-confessed Coronation Street superfan - who captured the nation's hearts last year for a touching act of love for his mother - gathered in his hometown of Stockport to share memories about his life.
Martyn was among 22 people killed by a suicide bomber at Monday's Ariana Grande concert.
Martyn's brother, Dan, wore a t-shirt showing his picture, which included quotes from celebrities who paid tribute to him.
Friends held up each of the letters of the word 'iconic' to remember the 29-year-old PR manager.
At the event, Martyn's partner Russell Hayward told the crowds that he gave him "so much joy and laughter".
"The pain I felt when I found out the news this week completely tore my heart out, but I will not let that pain tear away any of our precious memories we've shared," Russell said.