The Lucksman is a nickname for the bow, The Huntsman, in the game Team Fortress 2.
While playing Team Fortress 2, Kootra used a vintage version of The Huntsman, a bow and arrow weapon for the Sniper, and is lucky enough to get a large amount of kills with it. Due to how much luck goes into it, Koots renamed it the Lucksman.
Contrary to popular belief, Kootra was not the first to call The Huntsman The Lucksman. People in the Team Fortress 2 community have used this nickname since the release of the bow back in 2009. This nickname is usually accompanied by rage after getting killed by a lucky arrow shot.
This nickname originated back in 2009 after the release of the bow, after players found out Snipers using this weapon could just spam arrows down a narrow, crowded hallway and get a lot of kills. Snipers could also just randomly shoot somewhere (like outside of the enemy spawn) and sometimes get an unfair kill since this is not a hitscan weapon and arrows have to travel and hit target (unlike other sniper rifles in the game, which are hitscan, meaning where you click is where the shot instantly goes).
Recently, Kootra has named his Vintage Huntsman "The Fate Changer", which is fitting as he is quite the fan of the movie "Brave", where one of his quotes "change yer fate!" had originated from. His skill at changing fates continues to grow as he practices with his bow in real life as well as in game.