This guide is an excellent help to newcomers, but there's a specific interaction that I've run into that multiple times that wasn't on the list...
1. There's a difference between a monster Buff and a monster Effect. Things like Divine Blessing, which alter the creature's stats, are buffs that can stack. Gravity Pull, Momentum, Immortality, and Adrenaline are all buffs, in the sense that they all stack. Monster effects however, work a bit differently. A creature can only have 1 effect/skill at a time, and if a creature already has a creature effect, giving it a new effect will remove the old one.
Examples. In a life deck, you have the scorpion, whose effect is to inflict poison on each attack. Giving the Scorpion Adrenaline will cause him to inflict multiple poison counters per turn. Giving a Scorpion the "Mitosis"ability will remove its venom effect (New scorpions made through mitosis will still have poison though.)
In a gravity deck, a Gravity shard destroys permanents to gain +0/15. Giving the shard the "Acceleration" effect will remove the ability to destroy permanents and heal itself (Though, a 0-30 with acceleration is a force to be reckoned with.) On the other hand, giving the shard Gravity Pull will -not- remove its health increase/destruction effect, allowing you to have a meatshield that heals for 15 damage per turn whilst stripping the enemy's field of all permanents (Both are useful.) Similarly, Ortyugh's "Devour" skill is unaffected by Momentum or Gravity pull, but will be removed by Acceleration.