Fighting types are an amazing offensive type. Dispite most of them being swallowed up by the higher tiers, NU is still left with a plethora of fantastic options for use. Able to hit a lot of common types super effectively with powerful moves like close combat, dynamicpunch, hi jump kick, and drain punch is no joke. Also, only having 2 weaknesses is nice. There may not be too many options, some things I added here just to kill space, but fighting types have stood out for a long while for their ability to deal with many of the great threats, and become some themselves.
The Big Three
Gurdurr
As the prevo to one of gen 5's first "lolbroken" pokemon, gurdurr acts just like his big brother. With a great attack stat and access to eviolite, gurdurr becomes a fantastic tank. He also gets Bulk Up to boost his attack and defense at the same time, as well as the coveted drain/mach punch combo. The icing on the cake is the ability Guts, which gives him an attack boost from the otherwise crippling status that plagues so many potential threats.
Sawk
Sawk can utilize choice items to punch massive holes in the opponant's team. With powerful moves like Close Combat and Earthquake, Sawk can smash through walls with his huge attack stat and solid speed. Unfortunately, scarf sawk JUST misses out on beating gorebyss after a smash. But it does get a nifty ability called sturdy, meaning it will always live a hit from full health.
Emboar
With low speed, mediocre defences (except HP) and crappy defensive typing, not to mention being the only fully evolved fire/fighting type in NU, Emboar doesnt exactly scream excellent pokemon. At first that is. However, stare into those offenses in awe as he fires off STAB flare blitz and superpower. As one of the few physical attackers that can stand up to Tangela, and come out at the end. Emboar also can be a mixed wallbreaker with cool options like scald, grass knot, fire/focus blast. Also, rhyperior2 (as I sometimes call it, seriously look at those sprites next to each other.) Will get even BETTER when the ability reckless is released. This will give a power boost to moves like flare blitz, head smash, and wild charge.
Not Bad...
Scraggy
Be cautious before posting hate comments, for if you do, a pack of angry Molks will be after you. But either way, the ghetto toddler is surprisingly viable. Able to set up reliably and rest off the damage is amazing. Also, access to drain punch allows him to heal semi-reliably. However, there are things that set it apart from gurdurr and throh. First, scraggy has Shed skin, so instead of boosting attack, the status could go away! Also, he has STAB dark type, giving him both an immunity to psychic, and near-perfect coverage with his STABs.
Throh
As Sawk's little bro, you would assume there would be more in common between them than their sweet wardrobe option. In fact, Throh shares more with Gurdurr than Sawk. He shares the Guts ability, Bulk Up, and just overall tankishness with Gurdurr. However, gurdurr focuses mainly on sweeping with his boosts, wheras Throh preferrs to abuse the near-exclusive move Circle Throw to rack up hazards damage on the opponant. He can then use Payback to avoid being walled by ghosts and psychics.
Machoke
Again, an NFE fighting type in NU. The vast majority of them are however. But this by no means says that Machoke is bad. With access to the exclusive ability No Guard and STAB dynamicpunch, Machoke fills a certain niche that nothing else in NU can fill. With a 100% accurate powerful STAB move that has a sweet secondary effect. This move, is Dynamicpunch (its only accurate with No Guard.) He also has access to priority and good recovery with resttalk. He can also run a Guts set, but it is extremely outclassed by Gurdurr in every way.
Combusken
He may share his typing with emboar, but they are very differant. Combusken received an amazing ability called Speed Boost and thus gained an ability to late game sweep. However, Combusken has essentially no bulk. Along with this, it is fairly weak without any offensive boosts. If you aren't going to set up, it is better to go special, physical otherwise because of swords dance. However, even with the intence speed it reaches after a few boosts, it is still bypassed by priority and quick scarfers (this due to his mediocre speed from before boosts).
Not Good...
Monferno
Monferno is one of the more interesting options on this list. It isn't good at offense, like one would first think. I mean, it SHOULD be, with access to moves like flare blitz, close combat, mach punch, etc. But it, unlike the other fire/fighting starters, monferno takes on more of a support role. Using his solid speed, monferno can work as a lead to set up stealth rocks, get hit down to a focus sash, endeavor something, and kill it with a mach punch. Unfortunately, that's all it can do.
Mienfoo
Again, there isn't much it can do. Regenerator is a nice toy, especially with U-Turn. But other than that, a scarf set might be decent, because Hi Jump Kick is just so strong, but mienfoo can either be slow or weak, whichever you want to go with.
Meditite
Another "joke", meditite could actually be decent. He was banned from little cup for a reason, right? Again, Hi Jump Kick is the prevailing factor, but this is coming from something with an ability that doubles his attack stat. I mean, there must be SOME power there?
...
Riolu
As the final option on this list, Riolu is another interesting option. He can troll the living hell out of the opponant with prankster copycat and roar/circle throw, providing hazards are up. But then again, Why?
The Big Three

Gurdurr
As the prevo to one of gen 5's first "lolbroken" pokemon, gurdurr acts just like his big brother. With a great attack stat and access to eviolite, gurdurr becomes a fantastic tank. He also gets Bulk Up to boost his attack and defense at the same time, as well as the coveted drain/mach punch combo. The icing on the cake is the ability Guts, which gives him an attack boost from the otherwise crippling status that plagues so many potential threats.

Sawk
Sawk can utilize choice items to punch massive holes in the opponant's team. With powerful moves like Close Combat and Earthquake, Sawk can smash through walls with his huge attack stat and solid speed. Unfortunately, scarf sawk JUST misses out on beating gorebyss after a smash. But it does get a nifty ability called sturdy, meaning it will always live a hit from full health.

Emboar
With low speed, mediocre defences (except HP) and crappy defensive typing, not to mention being the only fully evolved fire/fighting type in NU, Emboar doesnt exactly scream excellent pokemon. At first that is. However, stare into those offenses in awe as he fires off STAB flare blitz and superpower. As one of the few physical attackers that can stand up to Tangela, and come out at the end. Emboar also can be a mixed wallbreaker with cool options like scald, grass knot, fire/focus blast. Also, rhyperior2 (as I sometimes call it, seriously look at those sprites next to each other.) Will get even BETTER when the ability reckless is released. This will give a power boost to moves like flare blitz, head smash, and wild charge.
Not Bad...

Scraggy
Be cautious before posting hate comments, for if you do, a pack of angry Molks will be after you. But either way, the ghetto toddler is surprisingly viable. Able to set up reliably and rest off the damage is amazing. Also, access to drain punch allows him to heal semi-reliably. However, there are things that set it apart from gurdurr and throh. First, scraggy has Shed skin, so instead of boosting attack, the status could go away! Also, he has STAB dark type, giving him both an immunity to psychic, and near-perfect coverage with his STABs.

Throh
As Sawk's little bro, you would assume there would be more in common between them than their sweet wardrobe option. In fact, Throh shares more with Gurdurr than Sawk. He shares the Guts ability, Bulk Up, and just overall tankishness with Gurdurr. However, gurdurr focuses mainly on sweeping with his boosts, wheras Throh preferrs to abuse the near-exclusive move Circle Throw to rack up hazards damage on the opponant. He can then use Payback to avoid being walled by ghosts and psychics.

Machoke
Again, an NFE fighting type in NU. The vast majority of them are however. But this by no means says that Machoke is bad. With access to the exclusive ability No Guard and STAB dynamicpunch, Machoke fills a certain niche that nothing else in NU can fill. With a 100% accurate powerful STAB move that has a sweet secondary effect. This move, is Dynamicpunch (its only accurate with No Guard.) He also has access to priority and good recovery with resttalk. He can also run a Guts set, but it is extremely outclassed by Gurdurr in every way.

Combusken
He may share his typing with emboar, but they are very differant. Combusken received an amazing ability called Speed Boost and thus gained an ability to late game sweep. However, Combusken has essentially no bulk. Along with this, it is fairly weak without any offensive boosts. If you aren't going to set up, it is better to go special, physical otherwise because of swords dance. However, even with the intence speed it reaches after a few boosts, it is still bypassed by priority and quick scarfers (this due to his mediocre speed from before boosts).
Not Good...

Monferno
Monferno is one of the more interesting options on this list. It isn't good at offense, like one would first think. I mean, it SHOULD be, with access to moves like flare blitz, close combat, mach punch, etc. But it, unlike the other fire/fighting starters, monferno takes on more of a support role. Using his solid speed, monferno can work as a lead to set up stealth rocks, get hit down to a focus sash, endeavor something, and kill it with a mach punch. Unfortunately, that's all it can do.

Mienfoo
Again, there isn't much it can do. Regenerator is a nice toy, especially with U-Turn. But other than that, a scarf set might be decent, because Hi Jump Kick is just so strong, but mienfoo can either be slow or weak, whichever you want to go with.

Meditite
Another "joke", meditite could actually be decent. He was banned from little cup for a reason, right? Again, Hi Jump Kick is the prevailing factor, but this is coming from something with an ability that doubles his attack stat. I mean, there must be SOME power there?
...

Riolu
As the final option on this list, Riolu is another interesting option. He can troll the living hell out of the opponant with prankster copycat and roar/circle throw, providing hazards are up. But then again, Why?