B.E.S.

"B.E.S." (Bacterian Empire Ship), also known as "Giant Battleship" in the OCG, is a series of Monster Cards usually identified by having "B.E.S." in their card name, but also include Big Core. The B.E.S. cards are based on the bosses of the Konami video game Gradius. They were used by Lorenzo in the anime, and by Nathan in the GX Tag Force games.

Playing Style
The main strategy of this Deck is using Boss Rush's effect to Special Summon B.E.S. monsters as beatsticks. However this can be difficult in the early stages of the duel due to Boss Rush's ruling that it cannot be activated in the same turn that you have Normal Summoned or Set.

Key cards besides Boss Rush include, Skill Drain, Kaiser Colosseum, Card Trader, and cards similar to Pot of Avarice, especially Exodius the Ultimate Forbidden Lord. Skill Drain gives a very Anti-Meta feel to the deck since monster effects are negated (including the Core's destruction effect, making them last longer) and Kaiser Colosseum will slow down a lot of decks because of the low swarming rates of the Cores themselves, unless you can activate a second Boss Rush. Card Trader puts Cores back into the deck, since they only can be summoned by Boss Rush when in there. Pot of Avarice and Exodius the Ultimate Forbidden Lord are essential for getting your Cores back in the deck, since they can only be special summoned by Boss Rush while they are in the deck. Other helpful cards include Enemy Controller, Creature Swap, and Maxx "C", which really contribute to the Anti-Meta potential of the deck. Another card that could possibly be used with this style of deck, assuming the player is using several continuous spells, is Z-ONE.

One disadvantage for the Cores is that they are all level 5 and higher and require tribute fodder, except for B.E.S. Big Core MK-2 when you control no monsters. Cards that can assist with this include, The Tricky, Cyber Dragon, Gilasaurus, Frog Engine, Trap Monsters, and Mausoleum of the Emperor. Though multiple uses of Mausoleum of the Emperor can be dangerous to yourself if you are running Skill Drain.

Another disadvantage for the Cores is the mid to late game battles. Although in the early stages of the duel they have great attack stats, however when the stronger monsters start hitting the field the Cores simply cannot push through. Because of this, it is necessary to include cards such as Limiter Removal and Lightning Vortex. Also Limiter Removal drawback is minimal as long as you have Boss Rush on the field. Lightning Vortex is also helpful for sending Cores to the graveyard to be recycled by Pot of Avarice or Exodius the Ultimate Forbidden Lord. Though perhaps the most major drawback is Spell and Trap removal, which can make the Cores very prone to Lockdowns consisting of Spells and Traps. Although B.E.S. Tetran can destroy spells and Traps, it only works if it has counters which does not usually happen due to Boss Rush. Because of this it is good to include cards such as Mystical Space Typhoon, Dust Tornado, and Anteatereatingant. Anteatereatingant is great for removing your own Boss Rush if you need to Normal Summon or Set.

Other than Boss Rush being used as a beatstick generator, it is possible to hybridize the deck with a burn strategy due to Cyber Summon Blaster. You can also add Dark Room of Nightmare to increase the damage output since Cyber Summon Blaster's effect is minimal (300 LP damage to your opponent per special summon of a Machine type monster). Luckily the effects of multiple Cyber Summon Blasters can stack. Another helpful card is DNA Surgery, which can instantly turn any monster you special summon into Machines as soon as they are summoned, adding to the damage.

It is possible to add Synchro or Fusion Monsters for the Cores. Though if you are running Skill Drain it will be counter productive since most Synchros and Fusions (especially the Fusions) are only useful for their effects. Perhaps the most useful tuner for the Cores is D.D. Sprite though you will have to remove from play a monster on the field for a turn to special summon it, but it should be easy if you are using the Frog Engine since you can remove Ronintoadin or Treeborn Frog. If running the Frog Engine it is also possible to use Fishborg Blaster combined with Genex Controller and Genex Undine if you have a few Formula Synchrons.

For Fusions, your best choice is usually Cyber Dragon combined with Future Fusion, Power Bond, or Overload Fusion to summon the Chimeratechs since you are running mostly Machine monsters. A Fusion Boss Rush deck would have great synergy with the burn style of play by using DNA Surgery to turn any monster you special summon into a Machine (as well as your opponents), which will greatly increase the damage output of Cyber Summon Blaster. Then with all monsters on the field being Machines you can use Chimeratech Fortress Dragon to launch an OTK.

Example Decklist:
Monsters
 * Swap Frog
 * Dupe Frog
 * Treeborn Frog
 * Ronintoadin
 * Big Core
 * B.E.S. Tetran
 * B.E.S. Crystal Core
 * B.E.S. Covered Core
 * B.E.S. Big Core MK-2
 * Exodius the Ultimate Forbidden Lord
 * Anteatereatingant

Spells
 * Boss Rush
 * Card Trader
 * Gold Sarcophagus
 * Kaiser Colosseum
 * Monster Reborn
 * Limiter Removal
 * Lightning Vortex
 * Enemy Controller
 * Creature Swap

Traps
 * Skill Drain

Weak Against

 * Different Dimension (D.D.) Deck ("Boss Rush" does not activate if the "B.E.S." monster is not sent to the Graveyard)
 * Stall Decks that include cards such as Gravity Bind
 * Rock Deck
 * Bounce Deck
 * A sidedeck with cards similar to Magnetic Mosquito or Chimeratech Fortress Dragon
 * Naturia
 * Fortress Warrior

Non-Boss Rush B.E.S. Deck
B.E.S. monsters are useful in tight situations (Opponent has a strong monster, B.E.S. monsters can stick around for awhile.) however, the use of Boss Rush eliminates their ability to stay on the field. It is possible to build a competitive B.E.S. deck without having to use Boss Rush, and it's much simpler than you'd think.

Playing Style
The idea is to use Token Generators, such as Victory Viper XX03 and Lord British Space Fighter, and quickly pull out Tokens, which are often used as tribute fodder for your B.E.S. monsters. It is a simple strategy, but it can prove to be very effective if done correctly. A good strategy to use is to summon a Vic Viper and equip it with cards such as Axe of Despair and United We Stand. Use Vic Viper to destroy the opponent's monsters, and use it's effect to summon a Option Token (which has the same ATK and DEF as the Vic Viper). Attack with Token if needed, then next turn, you can use the Token the Tribute Summon a B.E.S. monster, then repeat the process.

Even though the deck has the ability to generate high level monsters quickly, it can sometimes be a slow starter. It is very important to include stall cards such as Scrap-Iron Scarecrow and Threatening Roar. Use them if you only have a Vic Viper and a Token generated by Power Capsule to pass your Opponent's attack and summon a B.E.S. your next turn. High DEF monsters (such as Moai Interceptor Cannons) prove to be very useful because they stay on the field long enough for you to tribute them. Also, B.E.S. Big Core MK-2 is a great starting hand draw. Even though it gains no counters when it's Normal Summoned, you can Normal Summon it without a tribute if you control no monsters, and it's high ATK discourages the opponent from attacking it to get rid of it. Tribute MK-II for a B.E.S., then use Monster Reborn or Call of the Haunted to bring it back.

Since Level 4 Tokens are almost always on the field, you can easily add Synchro or XYZ monsters to the deck.

Example Decklist:
Monsters
 * Big Core
 * B.E.S. Big Core MK-2
 * B.E.S. Covered Core
 * B.E.S. Crystal Core
 * B.E.S. Tetran
 * Victory Viper XX03
 * Lord British Space Fighter
 * DUCKER Mobile Cannon
 * Moai Interceptor Cannons

Spells
 * Swords of Revealing Light
 * Burden of the Mighty
 * Card Trader
 * The Shallow Grave
 * Power Capsule
 * Axe of Despair
 * United We Stand
 * Mage Power

Traps
 * Scrap-Iron Scarecrow
 * Mirror Force
 * Threatening Roar
 * Call of the Haunted
 * Token Stampede

Weak Against

 * Different Dimension (D.D.) Deck ("Boss Rush" does not activate if the "B.E.S." monster is not sent to the Graveyard)
 * Stall Decks that include cards such as Gravity Bind
 * Rock Deck
 * Bounce Deck
 * A sidedeck with cards similar to Magnetic Mosquito or Chimeratech Fortress Dragon
 * Naturia
 * Fortress Warrior
 * Skill Drain

Related
It should be noted that there are some cards, such as Brain Golem, that are bosses from Gradius, are not a part of this archetype.