Scorpion King is the first movie I think of when I think of D&D. I remember watching it in theaters my junior year with my best friends (and fellow gamers). Its the first movie I saw in theaters that made me want to go home and immediately play D&D. The movie is fun. It's not great cinema, but it's fun. To me it feels like a more light hearted version of Conan (which I realize sounds really strange).
I haven't used it much in gaming. I know their's a rogue scorpion class in Sandstorm. It looked really cool, but I rarely have games that are set in the desert for extended periods, so it just never seemed fitting to take. I did a Scorpion King post for Barbarians of Lemuria and I could see using it with Astonishing Swordsmen & Sorcerers of Hyborea.
I really enjoyed the movies theme song (and associated video). I used to listen to it while making characters to get myself in the proper "bad ass" mindset (keep in mind I was in high school).