When playing creatures in Magic, the most important thing they have are abilities. I mean – you could play a “vanilla” creature but without any abilities, it’s not that interesting to play. I want to talk about keyworded abilities. Abilities with keywords are printed with a keyword and either has reminder text showing what it does, or no reminder text, meaning you’d have to go to the Magic rulebook and memorize what it does. I will talk about different keyworded abilities here, and rank them each by tier. Tier 1 being the most powerful and valuable, and going down from there.
Tier 1 (very powerful)
Hexproof: A creature with hexproof cannot be targeted by your opponent’s spells abilities. This makes the creature very hard to remove and still usable by you.
Example: Geist of Saint Traft.
Indestructible: A creature that is indestructible cannot be destroyed by effects or lethal damage.
Example: Darksteel Colossus.
Double Strike: A creature that has double strike deals both first strike and regular combat damage, meaning it essentially deals double damage.
Example: Mirran Crusader.
Unblockable: Forget trample or flying, this is the ultimate form of evasion. Cannot be blocked, period.
Example: Invisible Stalker.
Infect: A creature with infect deals damage to creatures in -1/-1 counters and to players in poison counters. Meaning it permanently shrinks creatures and if a player has 10+ poison counters, they lose the game.
Example: Phyrexian Crusader.
Protection from all colors / everything: A creature with protection from all colors or everything means that they cannot be blocked, targeted by any colored spell, or dealt lethal damage by anything.
Example: Iridescent Angel.
Tier 2 (powerful)
Shroud: a creature with shroud cannot be targeted by spells or effects (including your own).
Example: Inkwell Leviathan.
Flying: A creature with flying can only be blocked by other creatures with flying.
Example: Hypnotic Specter.
Deathtouch: A creature with Deathtouch destroys any creature it deals damage to.
Example: Vampire Nighthawk.
Lifelink: Whenever a creature with Lifelink deals damage, you gain that much life.
Example: Rhox War Monk.
Regeneration: A creature with regeneration may be regenerated by paying its regeneration mana cost, meaning it doesn’t get destroyed at that time.
Example: Troll Ascetic.
Flash: A creature with Flash may be played anytime an instant can be played (this means on your opponent’s turn).
Example: Vendilion Clique.
Protection from a color: A creature with protection from a certain color cannot be dealt damage, blocked or targeted by sources of that color. ie. protection from red, protection from blue, protection from white, protection from green, protection from black.
Example: Sabertooth Nishoba.
Tier 3 (mediocre)
Trample: A creature with trample assigns leftover combat damage (damage over the blocking creature’s toughness) over to the defending player. Powerful with high power creatures, otherwise just mediocre.
Example: Abyssal Persecutor.
First Strike: A creature with first strike deals combat damage before creatures without first strike. Powerful with high power creatures, otherwise just mediocre.
Example: White Knight.
Haste: Creatures with haste can attack and tap the turn it comes onto the battlefield.
Example: Ball Lightning.
Landwalk: Creatures with landwalk of a certain type are unblockable as long as the defending player controls a land of that type. ie. forestwalk, plainswalk, islandwalk, swampwalk, mountainwalk.
Example: River Boa.
Wither: Creatures with wither deal damage in the form of -1/-1 counters. Basically, half of infect.
Example: Boggart Ram-Gang.
Vigilance: Creatures with vigilance don’t tap to attack (meaning they stay behind as a blocker as well).
Example: Serra Angel.
Cannot be countered: Creatures with this ability cannot be countered by spells and abilities. Great against decks using counters, otherwise useless.
Example: Great Sable Stag.
Well, that’s the roundup for keyworded abilities. In general, creatures with tier 1 abilities are more valuable than creatures with tier 2 abilities, and tier 2 over tier 3. But, it all depends on the creature, its casting cost, what other abilities it has, its power / toughness, etc. But I hope I helped some people build their decks deciding on which creatures to keep over others, using this article :).