Hey so id like to ask you to help me find out a champ for me, first off all i prefer champs that can have kills (i mean no supp or super tank), also have higher carry potential, ofcourse be fun to play and be not-bad in current meta and also not a very-frequent pick, i appreciate any help, im gold1 right now btw [zombie-brand-clap]
You won't find a main, you never do, your main will find you..
also not a very-frequent pick
Sorry to say, this isn't going to work. Every champion that falls within your selected criteria are very frequent picks, because assassins are extremely strong atm. You can either be a sheep and play meta stuff and get easy wins, or play what you want and lose ~50% of your games. All this being said, I'd suggest 
. She's one of the lesser played assassins, but still has high carry potential.
Nasus, but only if you can stand farming. If you get good at stacking by late game you'll be 2-3 hitting towers.
