The most dangerous and deadly adversaries of justice stand ready to run amok
Perhaps one of the most well-known and most played card that lets you do this is Aether Vial, a Modern all-star that you can tap to put a creature into play from your hand so long as that creatures mana value equals the number of charge counters on it, which you can choose to add at the start of your turn
(If this creature isn't monstrous, put X +1/+1 counters on it and it becomes monstrous.) If Maester Seymour is no longer on the battlefield when its first ability resolves, use its power as it last existed on the battlefield to determine how many +1/+1 counters to put on the target creature
It does not have an overly outlandish visual, and yet the corals, details of the coin-like ornaments, and the prismatic scales complement each other very well
The Most Expensive Card: The Pristine Alpha Black Lotus holds the all-time record at an estimated $3,000,000