Is there a champion that can outrange turrets without Firecannon?

Senna, as of patch v10.20, can damage a turret outside its range with enough Absolution (passive) stacks.

Considering a turret's attack range is 750 and Senna's base attack range for Piercing Darkness (Q) is 600, it takes 120 Absolution stacks to have the same attack range of a turret and 140 to outrange it, since Senna gains 25 bonus range for every 20 stacks.

In this patch no, the only one that used to do it was tristana but they nerfed it.

You can compare every range with tower range and you'll see that noone outrange towers.

bonus : Still, some adc like caitlyn or tristana have higher range that allows to hit baron nashor or drake from the other side of the pit using specific spots.

I don't believe there are champions, this patch, that can outrange a turret. When they came out with rapid-fire cannon, the picture they used for an example of it was Tristana, firing a shot at a turret from way out of its range. Although, I believe there are a few champions who come very close:

• Jinx (when using fishbones, she can hit the turret from the very edge of the turret range)
• Tristana
• Twitch (according to the answer above)
• Caitlyn, pretty high range, but I haven't tested how ranged she actually is, but she starts out with the highest base auto attack range in the game, surpassed by tristana later in-game.

Kindred with enough stacks can because they are infinite.