Striking Sliver

Sliver creatures you control have first strike. (They deal combat damage before creatures without first strike.)

Sidewinder Sliver

All Sliver creatures have flanking. (Whenever a creature without flanking blocks a Sliver, the blocking creature gets -1/-1 until end of turn.)

Sinew Sliver

Hollowhead Sliver

Sliver creatures you control have "{T}, Discard a card: Draw a card."

Cautery Sliver

All Slivers have "{1}, Sacrifice this permanent: This permanent deals 1 damage to any target."
All Slivers have "{1}, Sacrifice this permanent: Prevent the next 1 damage that would be dealt to target player, planeswalker, or Sliver creature this turn."

Cloudshredder Sliver

Sliver creatures you control have flying and haste.

Lavabelly Sliver

Sliver creatures you control have "When this creature enters, it deals 1 damage to target player or planeswalker and you gain 1 life."

Two-Headed Sliver

All Sliver creatures have menace. (They can't be blocked except by two or more creatures.)