rules:
only 1 trope per series
only one series/sub-series per entry
nothing that has named or codified a trope (like magikarp power in pokemon red and blue for instance)

10:getting crap past the radar, wario: master of disguise
literally! in this game, whenever wario messes up a painting as artsy wario, it becomes sentient poop that walks off-screen! this is required to beat a boss, quite surprisingly.

9:the computer is a cheating bastard, super mario kart.
the mario kart series has LIVED off this trope for years, but the original SMK stands out as the worst
A:rival racers that almost always beat you
B:items that don't disappear like bananas and only CPU's can get
C:better driving than what the player has via wonky controls.

8:darker and edgier, pokemon X and Y
ancient war, nukes, the extinction of nearly everything, evil cults with ulterior motives, need I say more?

7:up to eleven, fire emblem: thracia 776
the fire emblem series is known for being nintendo hard, but DAMN!

6:unexpected shmup level, kirby's adventure/nightmare in dream land
the game was the first kirby game to use this as a tradition for the series' final boss battles