Seize the Initiative

Target creature gets +1/+1 and gains first strike until end of turn.

Saberclaw Golem

{R}: This creature gains first strike until end of turn.

Semblance Anvil

Imprint — When this artifact enters, you may exile a nonland card from your hand.
Spells you cast that share a card type with the exiled card cost {2} less to cast.

Silver Myr

Snapsail Glider

Metalcraft — This creature has flying as long as you control three or more artifacts.

Soliton

Steel Hellkite

Flying
{2}: This creature gets +1/+0 until end of turn.
{X}: Destroy each nonland permanent with mana value X whose controller was dealt combat damage by this creature this turn. Activate only once each turn.

Strata Scythe

Imprint — When this Equipment enters, search your library for a land card, exile it, then shuffle.
Equipped creature gets +1/+1 for each land on the battlefield with the same name as the exiled card.
Equip {3}

Strider Harness

Equipped creature gets +1/+1 and has haste.
Equip {1} ({1}: Attach to target creature you control. Equip only as a sorcery.)

Wolf

Sword of Body and Mind

Equipped creature gets +2/+2 and has protection from green and from blue.
Whenever equipped creature deals combat damage to a player, you create a 2/2 green Wolf creature token and that player mills ten cards.
Equip {2}

Sylvok Lifestaff

Equipped creature gets +1/+0.
Whenever equipped creature dies, you gain 3 life.
Equip {1}

Soul Parry

Prevent all damage one or two target creatures would deal this turn.

Sylvok Replica

{G}, Sacrifice this creature: Destroy target artifact or enchantment.

Throne of Geth

{T}, Sacrifice an artifact: Proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Tower of Calamities

{8}, {T}: This artifact deals 12 damage to target creature.

Trigon of Corruption

This artifact enters with three charge counters on it.
{B}{B}, {T}: Put a charge counter on this artifact.
{2}, {T}, Remove a charge counter from this artifact: Put a -1/-1 counter on target creature.

Scars of Mirrodin