Marble Palace - Gold/Silver/Crystal Guides

Fighting

Fighting is one of GSC's most interesting types. Their weakness to Psychic hinders them more than anything else; their Flying weakness rarely comes into play except against a Lugia, Zapdos, or Skarmory and the occasional Dragonite (and maybe Xatu or Crobat, but they've fallen out of the metagame generally at this time). Fighting specializes in Attack generally, and this stat should be its focus. Moves like Curse can be used to emphasize this stat and offer additional protection. Fighting types generally don't have a weak defensive stat, but they don't have a strong one either; they rely on their offensive capabilities to carve their way. They're used in a countering sense to take down Normals and Darks usually, and occasionally others such as Ice or elemental Flying or Gengars if moveset variety permits.

In general, any Fighting that can learn Cross Chop should have it. Cross Chop is the Fighting move of choice; it's got a high base damage, decent accuracy, and a high CH rate to boot. This is great against Snorlax with Curse or Blissey with Reflect or Curse; they already have the type weakness, and the high CH rate can help break the defensive advantage. However, an important thing to remember using it is if they're at high enough health to survive a normal hit, beware Counter. You might want to throw Curse on Pokémon like Machamp so you can Curse first turn instead of attack; this ensures their Counter will fail and at the same time you can KO them in one hit so you won't have to worry about it again. Dynamicpunch and Submission are the other two Fighting type attacks of note; the former is powerful and the confusion is nice, but it's hard to rely on due to its 50% accuracy. Submission's accuracy is below normal, and it deals a substantial amount of recoil, so generally it should be used with care.

Primeape

Primeape's contribution to the Fighting type is its Speed. As the fastest Fighting Pokémon and a fast Pokémon overall, it can be used for first-strike attacks over Pokemon that a Machamp might be slower than. It boasts Cross Chop as its primary attack, and it can learn Reversal through breeding if you want to do an Endure/Reversal combination or whatnot. It can learn Rock Slide via RBY TM, and it can be bred or RBY TMed Counter, which can help support its bad defensive stats.
Best uses: Speed, Reversal

Poliwrath

As a Pokémon, Poliwrath revolves more around its Water type than its Fighting type in how you should play it. Its best Fighting moves are Dynamicpunch and Submission. It really shouldn't be rated as a Fighting typically because its most important weaknesses/resistances will revolve around its Water type, as well as its Water and Ice moves.
Best uses: As a Water type

Machamp

Machamp is the clear all-around Fighting guy. Fair defensive stats all around, Cross Chop, enormous Attack, Earthquake, Rock Slide, what's not to love about this guy? Typically Cross Chop/Rock Slide/Earthquake compose its first 3 moves, though this can be tweaked if needed. Encore, Curse, Focus Energy, Fire Blast, Light Screen, and Counter are all common fillers ofr the last slot. I personally prefer Curse for the reasons mentioned in the introduction with Countering Normals.
Best uses: All-around great Fighting Pokémon

Hitmonlee

Hitmonlee in general is a mediocre Fighting type. Its Special Defense is a bit above Primeape's, as is it's Attack, but its Speed and Defense losses generally make up for it. Hi Jump Kick has higher accuracy than Cross Chop, but does less damage and can miss as well. The main valid use for him is Reversal. To me, he's just a slower Primeape without Rock Slide.
Best uses: Reversal

Hitmonchan

Hitmonchan's a bit more solid in Defense than Hitmonlee, but other than that it has little going. It can use a Mach Punch/Curse combo to good effect if laid out right, but generally it's just not a very good Fighting choice.
Best uses: Curse/Mach Punch

Heracross

One of the most interesting Pokémon in the game strategicly, Heracross boasts more tricks than a swiss army knife (which, with his wings open, he resembles a lot). His Bug type makes for an interesting combination of Psychic and anti-Psychic, and helps give him an edge against Machamps especially. He's got an above-average Special Defense and a pretty decent Defense, so he's a prime canidate for a little Cursing. His Attack is great, and Megahorn, his exclusive Bug move, is powerful to boot. Reversal is his only Fighting move to speak of really, besides Counter, which might come in handy with his slightly lower Defense. Earthquake begs to be on this guy. Heracross has the perfect set of resistances to hold Machamp at bay, so that's one of his better uses, and with Megahorn he can hold off Psychics without Psychic or slowly ones like Exeggutor well. Just beware the Flying weakness...
Best uses: Anti-Machamp, anti-Exeggutor, good all-around Curser