Gate Smasher can be attached only to a creature with toughness 4 or greater.
Equipped creature gets +3/+0 and has trample.
2/25/2015 Gate Smasher’s equip ability can target any creature. However, if that creature’s toughness is 3 or less as the equip ability resolves, Gate Smasher won’t become attached to it.
2/25/2015 If Gate Smasher is attached to a creature whose toughness falls below 4, Gate Smasher will become unattached as a state-based action.