Samurai Champloo, Tenjou Tenge, Grenadier, Trigun, and Gungrave......the first two are samurai animes, the last three are gun animes (Grenadier has some nudity, so if you dont like that thing dont watch it).
Other animes that are good, but dont have samurais in them are: FullMetal Alchemist, Tsubasa Chronicle, and Chrno Crusade.
If you like hardcore violence and dont mind nudity, watch elfen lied. If you like music, watch Beck. I also reccomend the Final Fantasy movie if you have played FFVII and like the FF game series.
All the animes that I listed are very good, but the first 5 are the only ones (that I know of) that have samurais and gun users.
Whichever anime series you pick, I hope get around to seeing all the ones I listed, you wont regret in doing so, and enjoy.