I just ban Aatrox, since he's the first champion on the roster.
Some people want to face an "annoying" champion Zed or Yasuo. Honestly, TF shits on Zed in lane, start boots + pot 4, 2 armor runes. Take minion dematerializer (or the biscuit rune) and stopwatch. Build tabis > catalyst > armguard. Zed will never one shot you, in the early game. Harass lvl 1 when he goes for minions. Let him push, but once he's lvl 3 he'll be so low that you can just zone him completely off of farm. I think TF is the best counter to assassins in lane.
Cass shits on Yasuo or at least goes even once she gets tear and beyond. Bait Yasuo into jumping onto your wave to get to you. Wait for him to use his dash ONTO you before you throw out Q. Then, just kite his ass. You heavily outdamage him in extended trades, because he can't touch you once he uses his dash ONTO you (because you know that he can't dash again if he just used it on you, then you can just Q where he is standing). You can create distance between you and Yasuo from Q ms boost + PHASE RUSH. If he throws out windwall, you can still outmaneuver him, or force him to back the fuck up. When Yasuo throws out 3rd Q as Cass, press R since he will be facing you during that slightly long cast animation time. Throw out a w > Q > Espam = gg. If R is not up, just press w when he throws out 3rd q. He can't ult, and you can fuck him up.
Against Leblanc, play Syndra. The counterplay is to push against her (be mind of Jungler), since her waveclear is so shit, while using e to disengage any Q> w from her. Matchup is so easy, not even funny. When she Q you you know she wanna W. So just Q> W her. Even if you miss q, E will proc the stun. Make sure to aim your QE at her w pad if she does manage to tag you with QW, however.
Some people don't ban because they want to face an "annoying" champion. To be honest, facing a Zed, Yasuo, Leblanc makes the lane more fun for me. I personally hate farm lanes, and facing an assassin makes the game more fun, even if you occasionally get shit on. Because it feels good to be under pressure a lot, not just cruise through a boring laning phase. A Yasuo is not impossible to win against. Zed, is not impossible to win against. Syndra shits on Zed pre-6. Though after 6 you gotta be more careful.
Then again, I'm only gold elo, I've probably haven't met extremely mechanically talented Zeds, Yasuos, Leblancs. But this is my 2 cents on their counterplay.
Plus, you are going to face them eventually, so why ban them? The best feeling is to shit on these champions. Give yourself a chance!
Though, I mainly ban Zed if I am autofilled, since sometimes I do not want to deal with a Fed zed as Nidalee support....