Anime with guys battling each other using small cars with weapons The anime is set in a world where people duel each other by using small cars with weapons . They throw the cars into the arena and the cars attack each other. I distinctly remember a blue colored car and I think that is the hero's.
My guess is that you're referring to Crush Gear Turbo


From http://upload.wikimedia.org/wikipedia/en/9/92/CrushGearTurbo-Logo-DVDSrc.jpg


From http://de.crushgear.wikia.com/wiki/Datei:Crush_Gear_Turbo_2.png 


  The hero's name is Kouya Marino and your description of his appearance matches to an extent.