>>32189728I actually did calculations and based on episode appearances and usage, Greninja has definitely the longest tongue out there.
In pic related episode, Greninja uses his tongue to catch serena from falling. She falls for a couple of seconds and the Greninja actually jumps higher up and shoots out his tongue, wrapping it it around her thrice. Based on the fall time, distance and the amount of tongue coils, Greninja's tongue must be able to extend to 15 meters at the very least, all the while remaining completely prehensile.
That's not all. In one of the last episodes of the flare arc, Greninja catches Ash, Serena and Bonnie (at the very least 220 pounds) falling at terminal velocity with it. Therefore we can conclude that not only can his tongue extend over 15 meters, but it can also lift over a ton of weight.
Puny tonguelets, take notes. If you want to have all the bitches lusting after your divine oral endowment, this is how it's done.