I can only think of six, the other possibly being Dark Ritual - and if you think Ritual is a problem remember what's coming at the end of this list

ONE PIECE CARD GAME - JAPANESE Sale price$199.99 One Piece Card Game - The Best PRB-01 Booster Box [Japanese]Bandai Only 1 unit left Save $30.00 Sale price$169.99 Regular price$199.99 One Piece Card Game - The New Emperor OP-09 Booster Box [Japanese]Bandai Sold out Save $1.00 Sale price$8.99 Regular price$9.99 One Piece Card Game - The New Emperor OP-09 Booster Pack [Japanese]Bandai Sold out Save $10.00 Sale price$139.99 Regular price$149.99 One Piece Card Game - Carrying On His Will OP-13 Booster Box [Japanese]Bandai Sold out Save $30.00 Sale price$169.99 Regular price$199.99 One Piece Card Game - Heroines Edition EB-03 Booster Box [Japanese]Bandai Only 6 units left Save $18.00 Sale price$119.99 Regular price$137.99 One Piece Card Game - Protagonist Of The New Generation OP-05 Booster Box [Japanese]Bandai Sold out Save $10.00 Sale price$99.99 Regular price$109.99 One Piece Card Game - The Best Vol

They're used to play Limited formats, like Booster Drafts, as well as to build a collection of cards for use in Constructed formats, like Standard
When you do, you'll either unlock its related Secret Pack or potentially even be awarded with one free to open
Re:Dive - Hiyori (No.MT2437) (65 Card
Everyone makes memes about how Tinker lets you play a 11 attack 11 defense indestructible Darksteel Colossus on basically the third turn of the game, which is completely ridiculous and in most instances just instantly wins the game