If u want a simple info.. u can use weaps like:
For 1 target use weaps like Mechgun.. or some dual sabers like:
Serene Swan, Lindcray (female-human), Psycho Raven (male) Ten Years Blade or a more basic like Sange e Yasha or Jizai.
For multi target use weaps like:
Excalibur, Slicer of Vengeance, Frozen faust, Arrest faust, bomb chu, Vjaya, Crush Bullet and the "end-gear" Dark Flow.
For Bosses u can use some from the list above (Multi target)
But there are other good weaps. Not just these.