Toph, the First Metalbender

Nontoken artifacts you control are lands in addition to their other types. (They don't gain the ability to {T} for mana.)
At the beginning of your end step, earthbend 2. (Target land you control becomes a 0/0 creature with haste that's still a land. Put two +1/+1 counters on it. When it dies or is exiled, return it to the battlefield tapped.)

Darksteel Citadel

Blitzball

{T}: Add one mana of any color.
GOOOOAAAALLL! — {T}, Sacrifice this artifact: Draw two cards. Activate only if an opponent was dealt combat damage by a legendary creature this turn.

Darksteel Brute

Indestructible (Damage and effects that say "destroy" don't destroy this artifact.)
{3}: This artifact becomes a 2/2 Beast artifact creature until end of turn.

Darksteel Axe

Indestructible (Effects that say "destroy" don't destroy this Equipment.)
Equipped creature gets +2/+0.
Equip {2}

Arcane Signet

{T}: Add one mana of any color in your commander's color identity.

Bender's Waterskin

Untap this artifact during each other player's untap step.
{T}: Add one mana of any color.

Bonder's Ornament

{T}: Add one mana of any color.
{4}, {T}: Each player who controls a permanent named Bonder's Ornament draws a card.

Diamond Pick-Axe

Indestructible (Effects that say "destroy" don't destroy this Equipment.)
Equipped creature gets +1/+1 and has "Whenever this creature attacks, create a Treasure token." (It's an artifact with "{T}, Sacrifice this token: Add one mana of any color.")
Equip {2}

Nutrient Block

Indestructible (Effects that say "destroy" don't destroy this artifact.)
{2}, {T}, Sacrifice this artifact: You gain 3 life.
When this artifact is put into a graveyard from the battlefield, draw a card.

Darksteel Relic

Indestructible (Effects that say "destroy" don't destroy this artifact.)

Boros Keyrune

{T}: Add {R} or {W}.
{R}{W}: This artifact becomes a 1/1 red and white Soldier artifact creature with double strike until end of turn. (It deals both first-strike and regular combat damage.)

Darksteel Ingot

Indestructible (Effects that say "destroy" don't destroy this artifact.)
{T}: Add one mana of any color.