0-cost cards One thing that wont be included in the list are 0-cost cards, like Black Lotus, Lotus Petal, or Ornithopter
In my opinion, this advice does more harm than good
Recoil isn't technically a cantrip, but the discard effect makes it "free" and also opens up the possibility of it becoming removal if your opponent has an empty hand
Titan of Industry I have rarely seen Titan of Industry being cast for its actual mana cost, but that's only because people try to cheat it into play from either their library with cards like Transmogrify or from the graveyard with the likes of Unburial Rites
Once this equipment hits the field, your opponent now has to contend with your entire deck when it comes to possible interruptions even if youre just bluffing
Alternatively you may construct and test a deck with an online simulator, such as on the Dueling Book website (Dueling Network is down), before deciding to buy some cards