Weapon Surge

Target creature you control gets +1/+0 and gains first strike until end of turn.
Overload {1}{R} (You may cast this spell for its overload cost. If you do, change "target" in its text to "each.")

Typhoid Rats

Deathtouch (Any amount of damage this deals to a creature is enough to destroy it.)

Mountain

Virulent Swipe

Target creature gets +2/+0 and gains deathtouch until end of turn.
Rebound (If you cast this spell from your hand, exile it as it resolves. At the beginning of your next upkeep, you may cast this card from exile without paying its mana cost.)

Swarm of Rats

Swarm of Rats's power is equal to the number of Rats you control.

Swamp

Burglar Rat

When Burglar Rat enters, each opponent discards a card.

Bladebrand

Target creature gains deathtouch until end of turn.
Draw a card.

Bladed Pinions

Equipped creature has flying and first strike.
Equip {2}

Heightened Reflexes

Target creature gets +1/+0 until end of turn. Put a first strike counter on it.

Flaming Sword

Flash
Enchant creature
Enchanted creature gets +1/+0 and has first strike.

Rat Colony

Rat Colony gets +1/+0 for each other Rat you control.
A deck can have any number of cards named Rat Colony.

Voracious Vermin

When Voracious Vermin enters, create a 1/1 black Rat creature token with "This creature can't block."
Whenever another creature you control dies, put a +1/+1 counter on Voracious Vermin.

Hunter's Blowgun

Equipped creature gets +1/+1.
Equipped creature has deathtouch during your turn. Otherwise, it has reach.
Equip {2} ({2}: Attach to target creature you control. Equip only as a sorcery.)

Looming Spires

Looming Spires enters tapped.
When Looming Spires enters, target creature gets +1/+1 and gains first strike until end of turn.
{T}: Add {R}.

Reflexes

Enchant creature (Target a creature as you cast this. This card enters attached to that creature.)
Enchanted creature has first strike. (It deals combat damage before creatures without first strike.)