They can also end friendships if used a little too much, or if glee is exhibited while playing the card from the hand
(6/22/2015) If you activate Gideon's third ability and then damage is dealt to him that can't be prevented, that damage has all applicable results: specifically, the damage is marked on Gideon (since he's a creature) and that damage causes that many loyalty counters to be removed from him (since he's a planeswalker)
(2008-10-01) In a Two-Headed Giant game, after combat damage is dealt, Quietus Spike looks at that player's life total (which is the same as the team's life total) when determining how much life the team will lose, which basically means the team's life total is halved
When that is all you want then he is as good as it gets but those decks are measured by their weakest cards not their best
Another energy ritual, Motherlode, Excavator will usually give you about four to eight energy on average, when played in the late game
Be sure to look into more niche equipment, and be careful with legendary ones