Riddick is well trained with any kind of weapon that he can get his hands on, but his weapon of choice is undoubtedly a knife. Silent, quick, and deadly, in Riddick's hands the knife is a weapon that is a swift ender of lives. However, Riddick's most famous weapons are the Ulaks that he is seen using during his escape from Crematoria and the knives that the player receives in The Chronicles of Riddick: Assault on Dark Athena.
This is not to say that Riddick can't or won't use anything else. On the contrary he has been known to use anything from pistols, rifles, platypi, to necromonger gravity cannons, teacups, possibly a key and anything in between. But it should be noted that Riddick is an efficient killer even if he doesn't have a weapon."