i suggest bowser jr. nobody mains him except me, so your opponent might not know what to deal with. his neutral special can be charged up, and when it is, it can be very powerful. his down special summons a mechakoopa that can pretty much do you dirty work for you, sometimes. his up special is really great for recovery, although it can leave you vulnerable. his side special is great for mobility and his some knockback potential. the only thing bad about him is his final smash, which can either k.o everyone on screen, or not do a single thing. from my experience, anyway. that's why i would say to try out bowser jr. although, masterBK9_Gaming is completely correct, you should use whoever you want. this is all my personal opinion.