I have a fairly specific meaning in mind for this in that I do not mean the best card but instead am focusing on the functionality of the card as a Counterspell
Ungraded & graded values for all MTG LEA Magic Cards
Rakdos Sacrifice, Mardu or Esper Greasefang, Angels, and Fight Rigging decks are all options you can see in viable competitive play
If you prefer your defenses to come in the form of surprise spells, you could replace Aven Courier and Floriferous Vinewall with Simic staples such as Rapid Hybridization , Krosan Grip , Nature's Claim , or counterspells like Negate or Swan Song
Additionally, some opponents run tech cards like Blood Moon and Aven Mindcensor, which completely counter fetchlands
Here you have a full-on ultra deck built for players who want something flashier and stronger right out of the box