There are several Pokemon that are good with the STAB they get.
Uber class:
1] 
Porygon-Z: This Pokemon can run a Specs and STAB Boomburst in STABmons, which is unacceptably strong. Hence it was turned Uber.
2] 
Sylveon: Since Pokemon can also get moves that their pre-evolutions can get STAB from, Sylveon gets a Pixilated Boomburst, which is again, unacceptably strong. Hence in Uber class.
OU:
1] 
Scizor: This one has a lot going for it. First off it can get access to King's Shield, which is a boon for any physically defensive Pokemon. It can also use the slightly gimmicky Fell Stinger, which while not 100% reliable, will fetch a gigantic boost if it KOs a target. And then there is Gear Grind.
2] 
Ferrothorn: Also gets King's Shield and Spiky Shield to utilize. Gets Synthesis to heal itself back, which is completely terrible.
3] 
Breloom: Storm Throw Breloom always crits, that compounded with 130 base attack and Technician is bound to hurt a lot . It also gets Arm Thrust, which, like Bullet Seed, is also threatening.
4] 
Landorus-T: Imagine being hit by a Brave Bird from 145 base attack. Nothing to toy with. Can also utilize Spikes now.
5] 
Kyurem-B: This thing's power was completely off the charts anyway, but in STABmons, it gets Icicle Crash. Nothing more to say.
6] 
Gyarados: Same reasons as Lando, but this won't be as tragic.
7] 
Espeon: Eeveelutions all got a credit to Boomburst, which means this thing will hit like the devil and abuse it to the most. It also get's Shell Smash and Baton Pass, which is absurd. Psycho Boost is shattering when it comes from this thing as well.
8] 
Vaporeon: This is one of those Pokemon that can actually make use of Noble Roar, and then do the Shell Smash + Baton Pass trick quite easily.
9] 
Sableye: Prankster Dark Void is not something to mess around with at all. Nor is Destiny Bond, since Mega Banette is nowhere in STABmons.
10] 
Scolipede: While it can utilize Tail Glow/Quiver Dance itself, the ability to Baton Pass is what is monstrous. Attack Order is also a useful move to carry.
11] 
Conkeldurr: You don't want to see a High Jump Kick coming from this.
12] 
Heatran: The volcano Pokemon with Eruption. This thing hurts like a truck.
13] 
Latios/Latias: If there is anything it might drop Psyshock for, it has to be Psystrike. And Spacial Rend also comes into play here.
14] 
Azumarill: This thing's Explosion is the last thing you want to hear. Also it gets Crabhammer now.
15] 
Togekiss: Once Geomancy with Power Herb and this thing can make itself home.
16] 
Thundurus-T: Oblivion Wing is gonna be this thing's best way of healing.
UU:
1] 
Aerodactyl: This thing now benefits from Brave Bird/Head Smash + Rock Head. Now that is a demon straight out of Jurassic Park.
2] 
Alakazam: You can pretty much define it as the abuser of Psycho Boost or Psystrike.
3] 
Darmanitan: Sacred Fire + Sheer Force + Life Orb. If there's anything that makes you want to run for your scarfer, it has to be this. Otherwise V-Create is also used.
4] 
Celebi: Looking for a Seed Flare/Spore/Luster Purge user? Get it all in one in this small packet.
5] 
Victini: A full accuracy Blue Flare is all that needs to be said.
6] 
Wobbuffet: Psywave on this? Or even screens? This thing has a whole array of moves to choose from.
7] 
Gothitelle: Any and every Psystrike/Psycho Boost can hurt, but much more when you are trapped. Gothitelle knows that as well.
8] 
Lucario: Shift Gear is gonna become common with this. And now it can also use Secret Sword.
9] 
Hydreigon: Nasty Plot is this monter's thing. Use it. Maybe even throw in Spacial Rend and Parting Shot for more fumes on the opponent's side.
10] 
Forretress: If there was one entry hazard it didn't get, it is Sticky Web. And STABmons has provided that with a sloooow U-Turn as well.
11] 
Kingdra: Kingdra has sets through which it can crit every time. How does a critical hit on a Water Spout sound though? Hopefully the answer isn't needed.
RU:
1] 
Braviary: This thing can use Rock Climb with Sheer Force, and is probably the only Pokemon to ever do so. You can use Bounce + Sheer Force as well, but then switching is a problem. Shell Smash is also a thing though, especially with Life Orb.
2] 
Drapion: This scorpion got it's love in STABmons because of it's access to Coil. Now if you compound that with a prioritised Sucker Punch and a better accuracy Gunk Shot and Megahorn, and possibly Parting Shot, I don't even know why this thing is RU.
3] 
Electivire: Beastly Attack. Volt Tackle. I have nothing to say here.
4] 
Jolteon: Again, Eeveelution boons with Boomburst.
5] 
Whimsicott: Prankster Spore? Sure thing. Prankster Defog? Hell yeah. The list is never ending with this one.
6] 
Durant: Hustle boosted Megahorn is not enough, Hone Claws and Iron Tail should happen as well.
7] 
Sigilyph: All kinds of fun stuff, like Oblivion Wing and Psycho Boost/Psystrike.
8] 
Golbat: Unlike Crobat, it can utilize Eviolite, so it's actually a better user of Toxic Spikes.
9] 
Registeel: Oh my god. This thing is incomplete without King's Shield. And now it has it.
10] 
Yanmega: Quiver Dance is not the only move here, Tail Glow is equally terrorizing. If not more, that is. And now Aeroblast is the new move it can use. gg
There are plenty more, but in my opinion these are all of the major ones.
I've never done NU before though, so this is as far as I will go (just saw that it was a thread xD)
Hope I helped!
