Satyr Piper

{3}{G}: Target creature must be blocked this turn if able.

Irresistible Prey

Target creature must be blocked this turn if able.
Draw a card.

Darksteel Myr

Indestructible (Damage and effects that say "destroy" don't destroy this creature. If its toughness is 0 or less, it's still put into its owner's graveyard.)

Compelled Duel

Target creature gets +3/+3 until end of turn and must be blocked this turn if able.

Enlarge

Target creature gets +7/+7 and gains trample until end of turn. It must be blocked this turn if able. (A creature with trample can deal excess combat damage to the player or planeswalker it's attacking.)

Emergent Growth

Target creature gets +5/+5 until end of turn and must be blocked this turn if able.

Goldenhide Ox

Constellation — Whenever Goldenhide Ox or another enchantment you control enters, target creature must be blocked this turn if able.

Anzrag, the Quake-Mole

Whenever Anzrag, the Quake-Mole becomes blocked, untap each creature you control. After this phase, there is an additional combat phase.
{3}{R}{R}{G}{G}: Anzrag must be blocked each combat this turn if able.

Predatory Impetus

Enchant creature
Enchanted creature gets +3/+3, must be blocked if able, and is goaded. (It attacks each combat if able and attacks a player other than you if able.)