The 38-year-old former sniper, who also appeared on celebrity U.S. reality show Stars Earn Stripes, was shot dead by fellow war veteran Eddie Ray Routh at a gun range in Dallas, Texas on 2 February (13).
His life was celebrated by over 7,000 friends and family members during a ceremony at Cowboys Stadium, where Travis sang a touching rendition of Amazing Grace, as well as his hit Whisper My Name.
Meanwhile, Nichols belted out his popular tune The Impossible, and his widow and mother of their two young kids, Taya Kyle, delivered a special speech.
Remembering her tragic husband, she said, "You taught me innocent, reckless love without abandon. You taught me how to turn a life full of fear into a life full of faith. You taught me that I could be more independent than I ever wanted to be. You taught me how to raise children with love and softness and proved it could be done with a high standard of respect and old-fashioned values."