Many archetypes have their own specific Extra Deck cards that can be used as part of your endboard or as a way to break your opponents board
For example, Normal Summoning White Tiger Summoner will allow you to also Special Summon one level 4 or lower Normal monster from your hand - effectively doubling the amount of summons you have made in a turn
Pulse of the Fields Lightning Helix Sorin Markov Griselbrand Sphinx of the Steel Wind Knight of Meadowgrain Swords to Plowshares Obstinate Baloth Ivory Tower Pelakka Wurm Pelakka Wurm was popular in Reanimate decks for a decent period as he would give a big immediate life return while also being an OK threat with a bit of extra value should they answer it
add it to your hand, then, if you added a Plant monster whose original Level is 7 or higher, you can send 1 Plant monster from your Deck to the GY
Its a racing set, and this is amazingly replicating the look of a Hot Wheels blister card, down to the price tag as power and the printed cutout for hanging displays
Famously synergizing with Fireball, this combo enabled worryingly consistent kills on as early as turn one in Vintage