Grand Vizier now prevents yourself from using the newly acquired gold, except by itself (and optionally with a random card from the deck).
Hand: GV GV Copper Copper Estate. Play GV, trash Copper&Estate, Play GV, Gain Gold to hand, discard Gold and Copper to draw a random card & give opponent Copper to hand.
Hand: GV Warehouse Copper Copper Estate. Play Warehouse, draw Copper Estate Silver. Discard Silver, Copper, Copper. Play GV, You now have 3 cards in hand, so only trash 2 estates.
Hand: GV Copper Copper. You have been hit with Militia. Play GV, gain Gold to hand, trash 2 coppers, buy $3 cost.
Hand: GV Hamlet Copper Copper Estate. Play Hamlet, draw copper, discard 2 coppers. Play GV, gain gold to hand, trash copper estate, buy $4 card.
Hand: GV Hamlet Silver Silver Estate. Play Hamlet, draw copper, discard 2 Copper&estate. Play GV, gain gold to hand, discard 2 silvers, draw something, buy $3+something card.