George Strait. There is a reason he's called the King of Country Music. Personally, I really like his older stuff; 80 proof bottle of tear stopper, they call me a fireman, unwound, oceanfront property in arizona, all my exes live in texas, cherokee maiden (I can tell you that song is a b***h to play on the guitar), etc.
I love pretty much all songs by Tim McGraw, Toby Keith, and Josh Turner. There are some songs by Kenny Chesney and Brad Paisley that I like too.
Going back farther, you've got emmylou harris, george jones, johnny cash, tammy wynette, etc. If you want to go really country, check out some stuff from really back in the day like Marty Robbins (he's got a lot of gunfighter and cowboy songs that I absolutely adore) and Bob Wills. THAT's country music.