Well here's a bunch of them:
HGSS-on
ReshiPhlosion- Used Typhlosion Prime from HGSS to power up Reshiram BW for VERY consistent BlueFlares.
CaKE (Cobalion NV, Kyurem NV, Electrode Prime)- Used Electrode Prime as energy acceleration to power up Cobalion or Kyurem T2 depending on the matchup.
PrimeTime- Used Yanmega Prime, Magnezone Prime, and Kingdra Prime to take quick KOs and big KOs with Magnezone. Yanmega could attack for no energy, Kingdra only needed one, and Magnezone could OHKO anything with Lost Burn while using Magentic Draw pokepower to draw and Kindras Spray Splash make sure of KOs.
CMT (Celebi Prime/Mewtwo EX/Tornadus)- Used Celebi to power up Mewtwo EX or Tornadus very quickly. Extremely fast, but somewhat low damage and can be inconsistent.
ZPST- Used Pachirisu CoL and Shaymin UL to power up Zekrom BW or Tornadus EP as early as T1. Fast but vulnerable and inconsistent.
Durant NV- Used Catchers and Hammers to disrupt your opponent while decking them out with Durant. Twins and Rotom UD were amazing in here to get what you needed. Very fun, ultra consistent with Revive, and one of my favorite decks in HGSS on. Various techs like Bellsprout TM or Smoochum HGSS were used for certain matchups.
Donphan Prime/Mewtwo/Rocky Helmet or Donphan/Dragons- Fast, bulky attacker in Donphan Prime while winning the Mewtwo Wars with Rocky Helmet and Mewtwos. Put damage on Reshis, Zekroms, or Kyurems to outrage depending on type matchup.
Gothitelle EP/Reuniclus BW- Faster, less bulky, one sided trainer lock The Truth deck. Used Gothitelle to sweep while Reuniclus cleared of damage and removed it with Blissey Prime HGSS or Max Potion.
Chandelure NV/Vileplume UD/Dodrio/Blissey- Used multiple Chandelures to do damage, Blissey to heal of damage, Vileplume to trainer lock, and Dodrio for retreat. Abused the heck out of Tropical Beach and Twins and Pichu HGSS.
Quad Terrakion NV- Curran Hill invented this during States and led it to a win I think. Used Terrakions to attack with EXP Shares as energy acceleration and got off consistent Retaliates. Very consistent.
ZekEels- Zekeels was Zekeels and nothing more.
Darkrai variants- Focused on T1 or 2 Darkrais while abusing Smeargle UD/Col to get as much draw as possible. Defenders + Eviolites countered Terrakions as well as Tornadus EXs.
Mew Prime/Accelgor DE/Vileplume UD/Chandelure NV/etc- The lock deck that worked the best (other than Frillish). When set up, as long as the player got consistent Deck and Covers with Mew Prime copying Accelgor, the lock stayed and if the player was smart, they would win. Had problems with Time. Used Chandy to have the KOs always go into your turn. Very fun, very good, should have won Worlds lol.
Zekeels/Terrakion- Exactly what it was
MewtwoEels- Exactly what it was
Klingklang- Big EXs with Klingklang BW, Max Potions, Prism, Rainbow, won Nationals in Masters somehow
Quad Entei EX- Won Canadian Nationals I think. Used Entei to attack (very bulky) and healing cards to tank. Entei could accelerate to other Enteis.
Very annoying, yet fun. Yes I like annoying decks.
MagneBoar- Emboar was used to accelerate fires to the field and Reshiram and Magnezone were used to hit for damage. Ran out of energy pretty quickly.
Reshiboar- Emboar accelerated to Reshiram
Landorus/Terrakion- Used Landorus NV for acceleration and speed, Terrakion for bulk and damage
Hammertime- Darkrai/Sableye/Hammers Disruption and consistency
I think that's all for HGSS....
MD-On
Staples- Uxie let you draw until you had 7 when you played it down. Azelf let you look at your prizes and replace a card from your hand with a pokemon you found there. Broken Time Space allowed for faster evolving
Machamp SF- Used Take out to Auto KO any basic and donk. Extremely fast.
SP variants- took easy KOs, very fast, very strategic. Garchomp C lv.X healed off damage on SPs, Luxray GL Lv.X had a catcher like ability and did 60 for 2. Energy Gain was a tool that counted as a colorless energy when attached to SPs. Crobat G did more damage when placed down, Poketurn returned SPs to your hand, Cyrus Conspiracy made the deck, and there were countless other cards that made these decks great.
Popular ones were LuxChomp, DialgaChomp, BlazeChomp, BLG, RogueChomp, and more...
VileGar- Used Vileplume UD and Spirtiomb AR to lock trainers and dealt massive damage through Shadow Room and Poltergeist from Gengar SF. Very strong, especially with Fainting Spell (when Gengar is KOd from damage, you flip a coin and if heads, your opponent's active is KO'd.)
Gyarados SF- Discard Magikarps, do damage. Very fast, very consistent, definitely one of the Tier 1s. Did the damage for 0 energy, so it could abuse SSU and Rescue Energy and Broken Time Space.
Drapion SF/Vileplume UD- Trainer lock along with Drapions sniping and lock and special conditions.
SableDonk- Donk deck, caused the mid season rotation. That's how broken it became.
Sablelock- Used Cyrus's Initiative to disrupt. idk what else about it really, never understood how it won....
MewPerior- Used Mew Prime to copy Rhyperior Lv.Xs attack and do massive damage , OHKOing everything. Had major problems with Dialga G Lv.X, so some variants used Blaziken FB, which doesn't help all that much.
Machamp SF/Vileplume UD- Luxchomp counterdeck. Damage and lock respectively.
Regigigas Lv.X- Regi was used to tank and used promo Regi to Drag off either big retreat pokemon or easy KOs. Had built in acceleration and healing.
Kingdra LA- Used Kingdra to deal quick, hard damage with both Kingdras (LA and Prime)
and many more! Such a great format where rogues could exist without being stomped on. Donphan Prime was popular too.
MagneRock- Used Regirock LA for acceleration and Magnezone Prime for attacking with Lost Burn
LostGar- Overhyped by Japan, tried to get 6 pokemon in your opponent's Lost Zone to win the game with Lost World.
DP-on
Claydol GE was THE best support card other than Uxie.
All that I know
Gardy Gallade- Gardevoir for Psychic Lock to stop Powers and Gallade to do massive damage.
Gengar AR/Spiritomb- Gengar uses Shadow Skip into Spiritomb AR to lock trainers. Sometimes used Dusknoir DP to remove support pokemon from play.
Sceptile/Leafeon- Used Sceptiles to have grass doubling and Leafeon for more acceleration. Leafeon hit for massive damage.
Charizard AR- Hit for big damage with each fire in play and sometimes used Ninetails for acceleration.
Salamence AR/SF/Delcatty- Used Salamence + Delcatty to accelerate energies into play and Salamence SF was used for quick, hard damage.
Kingdra LA
Machamp SF
Empoleon/Bronzong MD
Magnezone SF- Used Magnezone for acceleration, Magnezone Lv.X could move energies around and autoparalyze.
Gyarados SF-Had Felicity's Drawings to discard Magikarps.
Regigigas
So many more!