My two all-time favorites: Bob Marley & Lynyrd Skynyrd. I couldn't live without their music.
And then there is....

JamisonParker
hellogoodbye
Jack's Mannequin
Shiny Toy Guns
Scary Kids Scaring Kids
Silverstein
Funeral for a Friend
Hawthorne Heights
Willie Nelson
Saves the Day
Hank Williams(sr)
Johnny Cash
Odd Project
Seether
Something Corporate
Stephen Lynch
The Academy Is...
Tom Petty
Damian Marley
Cursive
Donovan Frankenreiter
The Allman Brothers Band
The Like Young


And I'll stop there... though I could go on longer, but I won't^^.