Pokémon Red and Blue/Route 24-25

'After you defeat Misty, you should head north from Cerulean City. Your rival, Gary, who now has four Pokémon, blocks the bridge. So do six members of Team Rocket. If you can defeat them all, you'll receive a valuable Nugget and the freedom to head to the end of this path, where you can meet the world's greatest Pokémon entusiast, Bill the Pokémaniac!'

The challenge of Nugget Bridge
Once you've thrown down your rival, you can reclaim Nugget Bridge by besting the six Jr. Trainers blocking your progress.

On the other side, Yellow players will find a man (at the yellow A) willing to give a a good home, while Blue and Red players will only find TM 45 which teaches Thunder Wave. It's a weak skill for winning battles, but good for disabling Pokémon to make them easy to catch.

More interesting is TM 19 in Route 25. You'll need to be crafty to get it: Be at least three squares below the Jr. Trainer number 7 who's blocking it when you cross his line of vision, and he'll abandon his post to come fight you. Immediately after, loop behind him and grab it.

It holds Seismic Toss, which does damage equal to the level of the Pokémon using it to an enemy regardless of their type or defense. Very cool!