Talon, Galio, Taric, Caitlyn, Heimerdinger, Morgana, Sivir, Karthus... There's probably more, but those are the most typical. Though, you have to remember Leblanc is very squishy herself, if you can survive her burst, you have a small window to do burst to her.
If I'm being counterpicked by LeBlanc I have a rune page filled with just Magic Resist runes, and I'll buy a Null Mantle to start giving me enough MR to resist her burst. I'll build a Chalice first, then continue my build as normal, and eventually finish into an Athena's unholy grail.
Leblanc, even when being counter picked, is such a tough middle to fight against. The thing about her is that she FALLS off hard mid-late game. Once laning is done, she's done. A good leblanc can kill a carry and die, but that's usually about all.
When playing against LeBlanc just focus on farming safely. I main Ahri and I get LeBlanc'd in the ass often on her, I generally just sit back and farm. I'll take Teleport so I can use all my mana to help me farm, go back and get my Chalice to farm even more, every now and then I'll get lucky and hit LeBlanc with some of my farm spells and get her low enough to dive on her with some CC.
Don't ever get cocky about a LeBlanc, even with near now life, she can silence, bind, and eat your entire life before you can get that one bar left on her. Don't dare go after her without CC, or you will pay. Unless you have enough to survive her burst, then you're okay, but she'll probably get away.
All that said, even counter picking her, LeBlanc owns mid. Its her lane, and she will win it if she's any good. She just doesn't teamfight well, its not her place.