Don't Have

Crush Underfoot

Choose a Giant creature you control. It deals damage equal to its power to target creature.

Getting

Blind-Spot Giant

Blind-Spot Giant can't attack or block unless you control another Giant.

Foriysian Totem

{T}: Add {R}.
{4}{R}: Foriysian Totem becomes a 4/4 red Giant artifact creature with trample until end of turn.
As long as Foriysian Totem is a creature, it can block an additional creature each combat.

Giant Harbinger

When Giant Harbinger enters, you may search your library for a Giant card, reveal it, then shuffle and put that card on top.

That's Mine

Create a Treasure token. (Then exile this card. You may cast the creature later from exile.)

Grabby Giant

Reach
{2}{R}, Sacrifice an artifact or land: Draw a card.

Grabby Giant // That's Mine

Have

Stinkdrinker Daredevil

Giant spells you cast cost {2} less to cast.

Fire Giant's Fury

Target Giant you control gets +2/+2 and gains trample until end of turn. Whenever it deals combat damage to a player this turn, exile that many cards from the top of your library. Until the end of your next turn, you may play those cards.

Furnace Host Charger

Haste
Mountaincycling {2} ({2}, Discard this card: Search your library for a Mountain card, reveal it, put it into your hand, then shuffle.)

Skyraker Giant

Reach (This creature can block creatures with flying.)

Sunrise Sovereign

Other Giant creatures you control get +2/+2 and have trample.

Giant's Ire

Giant's Ire deals 4 damage to target player or planeswalker. If you control a Giant, draw a card.

Mountain

Thundercloud Shaman

When Thundercloud Shaman enters, it deals damage equal to the number of Giants you control to each non-Giant creature.

Thriving Moor

Thriving Moor enters tapped. As it enters, choose a color other than black.
{T}: Add {B} or one mana of the chosen color.