Arneson, David Lance "Dave", n. (1947-2009) game designer and author, credited for creating the wold of Blackmoor, considered the first setting for Dungeons & Dragons, and helped create the system for the game with Gary Gygax in 1974.
Addendum: Dave Arneson often gets the short stick when it comes to getting the accolades for helping to create D&D, though many consider that the game would be quite different without his setting and rules. Gygax usually gets full credit in the general public eye, and until 3rd Edition was often the only person credited with creating the game.
Largely this stemmed from a legal battle between TSR and Arneson over who owned the rights to the game when the company put out Advanced Dungeons & Dragons, which they claimed was a completely new set of rules, rather than Arneson's claim that they built upon his original works.
He would continue to write for the business through the 80s and early 90s, working with TSR once again once Gygax became president of TSR to create the DA series of modules expanding on Blackmoor, later branching out to write an adventure for Shadowrun, DNA/DOA.
During the period he left TSR and after he stopped writing in the '90s, he went off to teach several subjects, including working with special-needs children and teaching computer game design.
Even with the legal battles considering his creation, Dave never lost the urge to game, spreading goodwill throughout his travels of the hobby (including espousing the ideas of polyhedral dice to help teach math and the educational benefits of role-playing), attending many conventions and generally slinging dice till he lost that last battle with cancer.
Though he didn't receive the same level of world-wide honors and mentions that Gary did when he passed a year earlier, he was still similarly honored with a front-page mention on the D&D website, honoring his contributions to the game and hobby.