Standard
- Vivi Ornitier is banned.
- Screaming Nemesis is banned.
- Proft’s Eidetic Memory is banned.
Pioneer
- Heartfire Hero is banned.
Legacy
- Entomb is banned.
- Nadu, Winged Wisdom is banned.
Historic
- Force of Negation is pre-banned.
- Frantic Search is pre-banned.
- Mystical Tutor is pre-banned.
- Entomb is pre-banned.
- Dark Depths is pre-banned.
Brawl
- Strip Mine is banned.
- Mana Drain is banned.
- Chrome Mox is banned.
- Ancient Tomb is banned.
Pauper
- High Tide is banned.
Chrome Mox is a permanent I’ve chosen to remove from my opponents’ boards many times.
It’s a ramp source you can play AND USE on T1, as well as every subsequent turn. Compare this to, say, Elvish Mystic, which can’t be used the turn it is played, or most mana rocks, which cannot be played T1. Something like Utopia Sprawl is a little more flexible than those other cards, in that you can play it on T1 if you want, but won’t get the ramp from it until later, or you can play it on a later turn and get the ramp immediately.
Chrome Mox is more powerful than any of those.