Splitskin Doll is one of the simplest, a 2/1 creature that lets you draw an extra card when it enters play, though it also forces you to discard one unless you control another creature with 2 or less power
Ardyn, the Usurper is definitely powerful though, and it can easily run away with the game if it sticks
Jeskas Will [The Most Flexible Ritual] Jeskas Will is the kind of red spell that turns a normal turn into a huge one
By percentage: Nanjamo (Iono) SAR at +116%, Pikachu AR (VSTAR Universe) at +111%, Pikachu ex SAR (MEGA Dream ex) at +89%
This can get silly and force you to discard a ton at the end of the turn, but if youre looking for specific cards, then the massive draw number is helpful
It gradually became more popular with time, to the point that there have been major national championships for the format since 2021