Edgewalker

Cleric spells you cast cost {W}{B} less to cast. This effect reduces only the amount of colored mana you pay. (For example, if you cast a Cleric spell with mana cost {1}{W}, it costs {1} to cast.)

Krosan Drover

Creature spells you cast with mana value 6 or greater cost {2} less to cast.

Stone Calendar

Daru Warchief

Soldier spells you cast cost {1} less to cast.
Soldier creatures you control get +1/+2.

Heartstone

Activated abilities of creatures cost {1} less to activate. This effect can't reduce the mana in that cost to less than one mana.

Sunscape Familiar

Defender (This creature can't attack.)
Green spells and blue spells you cast cost {1} less to cast.

Aluren

Any player may cast creature spells with mana value 3 or less without paying their mana costs and as though they had flash.

Auriok Steelshaper

Equip costs you pay cost {1} less.
As long as Auriok Steelshaper is equipped, each creature you control that's a Soldier or a Knight gets +1/+1.

Dream Chisel

Face-down creature spells you cast cost {1} less to cast.

Urza's Filter

Multicolored spells cost {2} less to cast.

Thunderscape Familiar

First strike
Black spells and green spells you cast cost {1} less to cast.

Thornscape Familiar

Red spells and white spells you cast cost {1} less to cast.

Helm of Awakening

Mana Matrix

Instant and enchantment spells you cast cost {2} less to cast.