Toxic Poison Sleeves are for players who love poison counters, toxic creatures and the thrill of slowly wearing down an opponents defenses
MTG isnt really built to allow for this physically (the ill-advised experiment with stickers in Unfinity notwithstanding), so this is a virtual change only that needs to be remembered by all players or signaled with a reminder or a written note
Sneak and ninjutsu usually aim to get creatures onto the battlefield at a cheaper cost
I already mentioned the two cards that deal best with split second cards, but I'm sure you can find others
The Forgotten Realms, for example, has every fantasy trope we could ever need when making a Magic set
Its sorcery speed, so you cant pull a removal on an opponents turn, but when it comes to you, if you have the mana, you can get out of any bind with this card