Paragon Path

Paragon Paths were a game mechanic introduced into the fourth edition of Dungeons & Dragons, replacing the concept of Prestige classes used in the previous edition. Whereas PrCs were optional sub-classes that you could take to make your character more powerful, Paragon Paths are effectively mandatory. You take a Paragon path at level 11, and it bolsters you from there to level 20 -- its next tier equivalent is the Epic Destiny.

Paragon Paths follow pretty standard motifs; they give two abilities at level 11, one passive and one triggered by spending an action point, and gain a third passive ability at level 16. They also gain an Encounter power at level 11, a Utility power at level 12, and a Daily power at level 20. There are exceptions, of course, but it's fairly standardized, easy-to-follow stuff.

Paragon Paths are generally sorted by class, but there are also a bevvy of racial paragon paths, and a few that are more open in membership.

Class-based Paragon Paths

Cleric

Angelic Avenger

You get to take on the aspect of angels, making you a much more deadly fighter. Angelic Action gives you a damage bonus when you spend an action point, Astral Vibrance lets you select Lightning, Radiance or Thunder at level 11 and deal that kind of damage to any bloodied enemy who gets too close, Weapon Training gives you free proficiency with a Heavy Blade type weapon, and Blood & Radiance means that any enemy that bloodies you is made easier to hit until the next turn. For powers, you get Astral Wave (a blast of damage based on your Astral Vibrance), Angelic Presence (scare the shit out of enemies for the rest of the encounter or until you get bloodied) and Angel Ascendant (smack someone for quintuple your normal weapon damage and gain the ability to fly for the rest of the fight).

Divine Oracle

Because of your divine connections, you're a prophet in the literal sense, making you capable of telling the future. In crunch, this means you can't be surprised (nor can any allies close by), you get to roll twice for your initiative, you get an extra move action when you burn an action point, and you get to roll twice when attacking against Will. For powers, you get Prophecy of Doom (bestow a free critical hit on a nearby target), Good Omens (you and any ally within 10 squares gets +5 to all D20 rolls for the next turn, but at the cost of being unable to inflict critical hits), and Hammer of Fate (big attack vs. Will, but if you miss, then you get to turn back time to before you used the power, at the cost of not being able to use this power again until the next encounter).

Radiant Servant

This is what you want if you're trying to play the Laser Cleric. You want to burn shit up with your beams of holy light, you take this fucker right here. Better chance of scoring critical hits with radiant powers, fry an enemy with ongoing radiant damage when you burn an action point, and undead & demons have a harder time shaking off your nasty mojo. For powers, you can disintegrate everybody around you with Solar Wrath, make a zone of holy light that heals your friends and fries undead & demons with Healing Sun, or shoot an enemy with a laser so strong that it then explodes into more lasers with Radiant Brilliance.

Warpriest

The blunt instrument of the PHB Cleric paths, this is for Clerics who know what they want; to get up in somebody's face, crushing skulls and ripping off balls and generally kicking ass for the lord. You deal more damage after using an action point, you can call for a reroll of a missed melee/close attack once per encounter, you get +1 to AC when wearing heavy armor, and you get a pseudo-marking ability that lets you stand in as a Defender. For powers, you get Battle Cry (smack a foe and let you & your buddies use a healing surge), Battle Favor (1/day you can regain HP as per two healing surges or recover a spent daily power by landing a critical hit) and Battle Pyres (zap all the fuckers around you, and then keep on zapping them with super-lasers until they shake off the divine target lock).

Fighter

Iron Vanguard

You specialise in taking a beating and being the last man standing. Heal hitpoints when you drop a foe, spend an action point for boosted defense or to take an action before falling unconcious at zero HP, and damage anyone you knock prone or push back. Naturally, its powers revolve around smashing enemies back with the weight of your body.

Kensei

Your basic samurai-inspired weapon master, with features revolving around getting suped-up benefits from a single specialty weapon of yours. You can strike for double damage with a Masterstroke, decrease incoming damage with Ultimate Parry, or zip across the battlefield hacking down up to three foes at once with Weaponsoul Dance.

Pit Fighter

Specializing in surviving no matter the odds, a Pit Fighter is a blunt and brutal opponent. For features, you get increased AC bonus, super-charge your damage when you burn an action point, and a general boost to damage. For powers, you get All Bets Are Off (hit the same target twice in a row), Deadly Payback (gain a temporary bonus to attack and damage against the last person to damage you), and Lion of Battle (quadruple damage and, if you drop your target, you can potentially spook all enemies nearby).

Swordmaster

Your basic Swashbuckler type paragon path. Quick, agile, and an expert with light or heavy blades. You get a bonus to AC and Reflex when you spend an action point, you can use the Containing Strike and Reaping Strike powers when you charge, and a critical hit with a light/heavy blade restores a depleted fighter encounter power. Precision Cut lets you strike for triple damage, Fantastic Flourish lets you mark a nearby enemy after you strike one, and Crescendo Sword lets you strike all the enemies next to you; hitting even one restores a depleted daily power, whilst missing still gives you back an encounter power.