This might not be quite what you’re looking for, but I always love it when you can become Super Sonic in those classic Sonic games. (And even Hyper Sonic, in the case of Sonic 3 and Knuckles.) This felt mind-blowing when it first happened in Sonic 2. Upon activating this power, you’re suddenly going faster (in a game that’s already fast), you’re jumping higher, you’re invincible, just plowing straight through all the enemies, and that energetic catchy tune is playing all the while… You are an unstoppable force! It’s definitely a reward that feels great to receive and utilize, after completing the optional but lofty task of collecting all the Chaos Emeralds.
What keeps Super Sonic from being too OP though is the fact it’s not permanent (it only lasts as long as you have rings, which steadily deplete), and if you’re not careful you can still die easily enough getting crushed by traps or falling into pits.
Pits that include… the infamous deep spike-floored one in Mystic Cave Zone. God help you if you fall in and you’ve got over a hundred rings.