Examples include Murder, Thoughtseize, Counterspell, and Path to Exile
It's a consistent source of land and tokens whose self-mill strategies synergize with a variety of decks
Holeutea is an extender that can be activated the turn its set by sending another trap from hand to grave, and can summon itself as a level 4 monster we can link off or XYZ summon it, or can be banished from grave to summon a Traptrix from grave
Spell Quick-Play During the End Phase of the turn this card was activated, add "Spellbook" Spells from your Deck to your hand, except "Spellbook of Judgment", up to the number of Spell Cards activated after this card's resolution, then, you can Special Summon from your Deck 1 Spellcaster monster whose Level is less than or equal to the number of cards added to your hand by this effect
I like it most when an attack can kill a player just with the triggers and not have to worry about losing creatures in combat