Maybe not every deck, but most decks anyways. Are there any cards that are just that good, that versatile, that you think should be staples in every deck? If so, what do you think those cards are? Give you take, let's see what we got here.
There are the obvious cards that have been used as staples forever, such as...
Swords of Revealing Light
Mystical Space Typhoon
Then we got the plethora of new cards that have worked their way up to core status...I don't even know where to start, I'm sure this list will fill up when discussion gets started.
Bottomless Trap Hole
Pot of Duality
I also have a personal set of favorites that I like to use, too much for one deck in fact! But I think a lot of these cards and combos are underrated.
Magical Cylinder - Negates an attack and inflicts the entire attack directly at their lifepoints!...you manage to use all 3 and you don't even need anything else!
Black Horn of Heaven - Counter trap that negates a special summon, no strings attached
One Day of Peace - Each player draws 1 card, and neither player takes damage until the end of the opponent's next turn. ...Buys yourself some time and an extra card to get out of a jam
Marshmallon - Yes I am that guy...but c'mon!
Metaion, the Timelord - One of my favorites. I don't know how many times this card has gotten me out of a jam...it just kicks so much ass. There are really only 2 threats to it, the commonly used Compulsory Evacuation Device, and the lesser used Dimensional Prison. This card is impervious to Mirror force, Bottomless Trap Hole, and Torrential Tribute. Here's the whole effect so you can see for yourself. Cannot be Special Summoned from the Deck. If you control no monsters, you can Normal Summon this card without Tributing. This card cannot be destroyed by battle or by card effects. You take no Battle Damage from battles involving this face-up Attack Position card. At the end of the Battle Phase, if this card attacked or was attacked: Return all other monsters on the field to the hand, and inflict 300 damage to your opponent for each card returned. During your Standby Phase: Shuffle this card into the Deck (even if face-down).
Waboku - An oldie but a goodie. Not many people use this card anymore, perhaps ya'll know it's old effect, but it got an upgrade a couple years ago, making it I think worthwhile to use again...You take no Battle Damage this turn. Your monsters cannot be destroyed by battle this turn.
Black Luster Soldier: Envoy of a New Beginning - Ya'll know what this does, definately worth having if you got a deck with a couple of light and dark monsters.
Schwartzchild the Limit Dragon - This card is brand spankin' new, and I think worth using in any deck with light level synchros. It's lacking in power, but it's level 8 and essentially brings itself out...If your opponent controls a monster with 2000 or more ATK, you can Special Summon this card (from your hand).
Tour Guide From the Underworld - To me, this card is basically a 1 card deck thinner that gets you a level 3 xyz. I like to pair it with (see below)
Wind-Up Zenmaines - Nothing to speak of in terms of power, but you basically get to destroy 2 of your opponents cards.