For the longest, perhaps still even now, Chandra was the most impactful of impulse draw cards
The Hippy, or hypnotic Specter from Fourth Edition, was given a partner in crime in Ice Age with Abyssal Specter and discard decks were furthered by Mind Warp and expensive version of Mind Twist from Fourth Edition
There is also Heartwood Storyteller, in my experience both belong in a deck with even more creatures but they could still be useful I think
Counter Blitz is the Final Fantasy 10 deck, and based on the game's sphere grid, which translates to Magic in the form of +1/+1 counters
Alpha is one of the hardest sets to get a pack of, and includes so many popular cards that the Alpha Dark Ritual is easily the most valuable one you can own
A reskinned card that functions as a Lightning Bolt spell takes on the title of the infamous Hadoken