Lazy but a genius? I'd say that Ryner Lute is a good fit for that description. Although perhaps talented is a better word for him? He's an expert in various fields and although his carefree attitude makes it hard to believe, he is fairly intelligent as well.
Ayumu Narumi from Spiral: Suiri no Kizuna.A genius and highly talented guy but due to his elder brother basically being better than him at everything, he lazes around and doesn't strive to achieve much. Then he goes around solving mysteries with his sidekick. I would recommend you to read the manga, the anime is a disappointing adaption.
Densetsu no Yuusha no Densetsu and Spiral are good suggestions as well.
Modified by lisnoire, 06-25-12, 9:01 AM
-animeS - The plural of anime is anime. More than one deer is still deer. There is no damn "s". -epic |ˈepik| noun•a work portraying heroic deeds/adventures covering an long period of time - adjective • heroic/grand in scale or character Active Military, Prior Service, and Veteran's Anime Club http://myanimelist.net/clubs.php?cid=25937&time=1299710079