• R/B
• G/S
• R/S
• D/P
• Strategy
• Moves

Machamp

In a game where Normal Pokémon dominate, Machamp is not a bad choice. Just be wary of the equally dominant Psychics. Paralyzing Psychics on switch-ins with Body Slam is always fun. Earthquake is for Gengar and versatility. Hyper Beam does a lot of damage as well, and is a great finishing move. Submission does more damage against Rock and Normal-types, but remember that the recoil hurts and the accuracy is less than ideal. However, in a pinch, feel free to throw a Submission for a quicker KO.

Other Options

Rock Slide can be used against Flying-types. Counter is an option against Pokemon such as Snorlax and Tauros. Since Machamp's Defense isn't huge and its HP is good, it will be able to use Counter well; just make sure you predict a Normal or Fighting attack, since in RBY, Counter won't work on other physical moves. Body Slam's ubiquity may help with that.

Opinion

Machamp is a good Pokémon. Give it some paralysis support and it can cause havoc. It has low defenses and Speed, so it definitely needs paralysis support to hurt teams. The lack of a better STAB move than Submission hurts him, as well as its typing in a Psychic-dominated metagame, but it can do great damage in the late game with some prediction.

Counters

Psychics like Alakazam, Starmie, Slowbro, and Exeggutor all switch into Machamp easily (Alakazam doesn't enjoy a Hyper Beam, however) and annihilate itm with Psychic, Surf, or Blizzard. Zapdos's super effective Drill Peck hurts Machamp a lot, as do the STAB attacks of Moltres and Articuno. The latter two must beware of Rock Slide, though. Venusaur is also a competent counter as it can take a hit, Sleep Machamp, and then start firing away with STAB Razor Leaf.