Legendary creatures you control get +X/+X, where X is the number of legendary creatures you control.
Whenever you cast a legendary spell from your hand, exile cards from the top of your library until you exile a legendary nonland card with lesser mana value. You may cast that card without paying its mana cost. Put the rest on the bottom of your library in a random order.

Equipped creature gets +2/+2 and has protection from black and from green.
Whenever equipped creature deals combat damage to a player, that player discards a card and you untap all lands you control.
Equip

Equipped creature has base power and toughness X/X, where X is your life total.
Equip

+1: Search your library for a Swamp card, reveal it, put it into your hand, then shuffle.
−3: Target creature gets +X/+X or -X/-X until end of turn, where X is the number of Swamps you control.
−6: You get an emblem with "Swamps you control have ': Add .'"

Landfall — Whenever a land you control enters, put a +1/+1 counter on target creature.
: Double the number of +1/+1 counters on each creature you control.

Flying
This creature enters with three +1/+1 counters on it.
At the beginning of your upkeep, you may remove any number of +1/+1 counters from this creature. If you do, create that many 1/1 colorless Tetravite artifact creature tokens. They each have flying and "This token can't be enchanted."
At the beginning of your upkeep, you may exile any number of tokens created with this creature. If you do, put that many +1/+1 counters on this creature.

Sneak (You may cast this spell for if you also return an unblocked attacker you control to hand during the declare blockers step. She enters tapped and attacking.)
When Elektra enters, destroy target creature an opponent controls with power 3 or less.

Equipped creature gets +2/+2 and has protection from green and from white.
Whenever equipped creature deals combat damage to a player, exile up to one target creature you own, then search your library for a basic land card. Put both cards onto the battlefield under your control, then shuffle.
Equip

Deathtouch
When this creature enters, the Ring tempts you.
Whenever the Ring tempts you, put a +1/+1 counter on each Wraith you control.
A deck can have up to nine cards named Nazgûl.

Equipped creature gets +1/-1.
Whenever equipped creature dies, draw two cards.
Equip

Enrage — Whenever this creature is dealt damage, create a token that's a copy of this creature.

Trample
Whenever this creature or another creature you control with power 4 or greater enters, you gain 3 life and draw a card.
When this creature dies, if it's not a token, create a token that's a copy of it, except it's an artifact in addition to its other types.

You may have Sakashima enter as a copy of another creature you control, except it has Sakashima's other abilities.
The "legend rule" doesn't apply to permanents you control.
Partner (You can have two commanders if both have partner.)

Search your library for an artifact or enchantment card, reveal it, then shuffle and put that card on top.

Indestructible
Once each turn, you may pay rather than pay the mana cost for a colorless spell you cast from your hand.

At the beginning of your upkeep, you lose 1 life and create a 1/1 black Faerie Rogue creature token with flying.

Black creatures get +1/+1.

, Sacrifice a creature: Scry 2.
, : Exile the top card of your library. You may play that card this turn. When you exile a nonland card this way, Hidetsugu deals damage equal to the exiled card's mana value to any target.

As Mimeoplasm enters, exile up to X creature cards from your graveyard. It enters with three +1/+1 counters on it for each creature card exiled this way.
: Mimeoplasm becomes a copy of target creature card exiled with it, except it's 0/0 and has this ability.

: Search your library for a Sliver card, reveal that card, put it into your hand, then shuffle.
: Gain control of target Sliver. (This effect lasts indefinitely.)