Frost Titan

Mana cost: {4}{U}{U}
Type: Creature — Giant
Power / toughness: 6 / 6
Set: Duels of the Planeswalkers 2012 Promos #1 (mythic)

Whenever this creature becomes the target of a spell or ability an opponent controls, counter that spell or ability unless its controller pays {2}.
Whenever this creature enters or attacks, tap target permanent. It doesn't untap during its controller's next untap step.

Frost Titan has 7 printings, first in Magic 2011 (2010). EDHREC ranks it #10,050 among Commander cards. It appears most in Hylda of the Icy Crown decks (3,690 on EDHREC). 1 public deck on TCG runs it. It has 4 official rulings.

Legality

commander: legal
legacy: legal
vintage: legal
pauper: not legal
modern: legal
pioneer: not legal
standard: not legal
brawl: legal

Public decks that run Frost Titan

Peer Through Time - Commander 2014, led by Teferi, Temporal Archmage

Commanders that run Frost Titan most

Deck counts from EDHREC.

Often played with Frost Titan

Cards that show up in the same decks on EDHREC.

Rulings

2010-08-15: Frost Titan’s first ability affects each spell (including Aura spells), activated ability, and triggered ability that’s controlled by an opponent and that Frost Titan becomes a target of.
2010-08-15: You may target any permanent with Frost Titan’s second ability. It’s okay if that permanent is already tapped.
2010-08-15: If the permanent affected by Frost Titan’s second ability is untapped at the time that permanent’s controller’s next untap step begins, the last part of Frost Titan’s second ability has no effect.
2010-08-15: If the permanent affected by Frost Titan’s second ability changes controllers before its old controller’s next untap step, Frost Titan’s second ability will prevent it from being untapped during its new controller’s next untap step.