Parker (no first name) is a thief and killer introduced by Donald Westlake (writing as Richard Stark) in 1962 in the action thriller The Hunter. Shot and left for dead by his partner (and his wife), Parker cuts a swath through New York's underworld to retrieve his money and have his revenge.
Westlake would go on to pen nearly twenty-five Parker novels (ending in 2008 with Dirty Money) and each one has a clever heist, interesting supporting characters (including the charming actor Grofield, the loyal Handy McKay, and the sultry Bette Harlow), and brutal violence.
The books themselves have been adapted to film sporadically over the years. The finest adaptation is probably Point Blank, the fantastic John Boorman adaptation of The Hunter that starred Lee Marvin and Angie Dickinson.
However, the series has been given a serious shot in the arm in the last few years by the immensely talented Darwyn Cooke. Shortly before Westlake's death, Cooke began adapting The Hunter to comics. It was a fantastic book (the first adaptation to use Parker's name, too) and successful enough to warrant a sequel. Cooke has indicated that, besides his already-completed versions of The Hunter and The Outfit, he will adapt The Score and Slayground. I can't wait.