I take back what I said about Giant being slow. It's not so much slow as it is hign maintenance in order to receive the good part of the effect. The high maintenance is having to buy another Giant and play it every shuffle. If you have 2 Giants in your deck, you get the attack and +$5 every shuffle. It's really like, if you played a terminal Copper previously, you get +$5 and a strong attack.
So, to get the good effect every shuffle, you'd have to buy a second Giant, which is really a $5 Abandoned Mine. You know what though, if I have lots of actions to spare I can afford playing an Abandoned Mine every shuffle. The benefit of doing so is a +$5 spike and an attack that, depending on the board, may be very unlikely to whiff.