Children of Mana is a hack 'n slash that you just go and fight herds of monsters over and over... and over... and over... and over. I liked it though, making enemies bounce off walls was fun in short bursts.
Ninja Gaiden and FF:CC RoF are good (however, I don't really like FF personally).
I got sick of FF though because of the ridiculously slow magic system, the retarded allies and the horrible, childish story. Honestly, can't a FF game have hack n slash gameplay and have a more mature story.
Get Ninja Gaiden, it is incredible. I rank it as second on my top 5 DS games. Incredible speed, it never slows down (FF does sometimes), because it uses pre-rendered backgrounds.
Rune Factory has hack n slash dungeon play, and amount of weapons is pretty deep. It is mainly a farm sim though, so don't expect a deep combat system.