There are at least three artists with the name Haymaker. 1. A hardcore/punk band from Hamilton, Ontario.
2. An Alt-Country/Americana band from Long Beach, CA.
3. A rock band from Seattle, Washington see Haymaker (seattle) - http://www.last.fm/music/Haymaker+%28seattle%29.
1. Haymaker is a hardcore/punk band from Hamilton, Ontario comprised of former members of Left For Dead, Chokehold, The Swarm etc. They are well-known for extreme shows which usually end with fights and injuries.

Read more about Haymaker on Last.fm.