Guild Wars 2

Core idea
Once you reach Lvl 80, you get a mail from your respective trainer asking for you to meet with them. They explain that you’ve gotten as good within your class as you could possibly get, however there’s now the option to seek out one of two masters of a Specialized aspect of the class, to learn their secrets and new abilities. You’d then find these people and be given a new set of “Duties” similar to Dailies, in that you have to clear 5 different tasks set by the Master. You can choose which set of duties, or Path , that fits you the most:

Path of the Adventurer: Tasks are Focused around PvE and Open-world.
Path of the Conqueror: Tasks are focused around PvP.
Path of the Defender: Tasks are focused around WvW.

Once you finish all 5 tasks and return to the Master, he then teaches you your new Specialization, which comes with a variety of new Utility Skills (And possibly a Trait tree) and weapon skills.

Warrior
Can become a Barbarian, which focuses heavily on Damage and all-out offense. They’d gain new Rage skills, which increases their offense further by paying a price in health, defense or other areas. They could use Shortbows and Torches as new weapons.
Can instead focus on becoming a Knight, which focuses mostly on defense and support. They’d gain new Rally skills, which are similar to Banner however they’re instead focused around the Knight themselves and offer a different buff, such as Increased Endurance regeneration, pulsing Condition Cleanse or increased Condition duration. Knights could use Pistols main and offhand as new weapons.

Guardian
Can become a Crusader, which uses their magic for a punishing offense to lock down and control enemies, gaining access to AoE burns, immobilizes and knockdowns with their new Condemnation skills. They’d gain Axes mainhand and Longbows as new weapons.
They could also become a Zealot, which gains powerful defensive and supportive skills in the form of Rituals, which are lengthy in cast-time and Cooldown, but make up for it by giving a Unique buff to the team which persists for quite some time and are meant to be cast before a difficult encounter. They’d gain the use of Daggers main and offhand.

Ranger
Can become a Beastmaster, in which they truly become one with their companion through Sacrifice skills, which drains the health of your pet and stows it away in return of great buffs to the Ranger themselves, or vice versa. They’d gain Rifle and Shield as new weapons.
They could also become a Druid, focusing on defensive and supportive magic with the help of Shamanism, calling forth the wind to block projectiles, or a cause the skies to crack into rain or lightning. They’d gain Staff and Scepter as new weapons.

Thief
Can become an Assassin, focusing entirely on destroying their enemies from stealth, without them ever knowing they were there. They’d gain new Assassination skills, which are offensive skills that gain increased potency from Stealth and sets them up for devastating, new stealth attacks. They’d gain Sword off-hand and Rifles as new weapons.
They could also focus on becoming a Warmonk, their new skills called Maneuvers being used to quickly regain lost initiative, endurance or resist damage and gain the upper hand. They could use Staffs and Axes main-hand as new weapons.

Engineer
Can become a Thaumaturgist, which mixes the technological advancements they’ve found with all manners of magical applications. They’d gain new Tool kits such as the Tesla Kit, which focuses on Control and overcharging turrets, as well as new Magitech which mixes magic and technology into marvelous (And possibly dangerous) contraptions. They’d gain Staff and Scepter as new weapons.
They could also forgo the hippietalk and become Warmongers, gaining new weapon kits such as the Multigun kit, an abominable lovechild of the Gatling gun and a Rocket launcher, as well as new Ammo skills which adds a specific flavour to each attack that the enemies won’t soon forget. They’d gain Hammer and Mace main-hand as new weapons.

Elementalist
Can become the mysterious Arcanist, who can conjure forth specific elemental Seals on the ground beneath their allies or enemies, granting Boons or strengthening Allies, weakening enemies with conditions or other crippling effects depending on their attunement. They’d gain Longbow as a new weapon.
They could also focus their efforts straight on the offense as a Battlemage, gaining access to a wide variety of new buffs in the form of Charms, that’re conjured forth and grants the wielder specific boons and empowers them as long as they remain active. They’d gain Sword main-hand and Shield as new weapons.

Necromancer
Can become a melee-focused Reaver, charging straight into battle with the help of their new Syphon skills, which drains large amounts of health from enemies, absorbs their endurance or boons, while severely weakening their prey and granting life force to the Necromancer. They’d gain Greatsword and Mace main-hand as new weapons.
They could also focus more on attrition as a Harbinger, using their new Stigma skills to brand an enemy with a specific, unremovable debuff that constantly applies crippling conditions to them for a short time, making escape very difficult. They’d gain Hammer and Axe off-hand as new weapons.

Mesmer
Can become a Minstrel, who can now summon specific Ethereal Instruments, which lands on a specific spot with an Illusion constantly playing a song that Strengthens allies and weakens enemies. If the Illusion is destroyed, the Instrument can be picked up as a bundle, and new illusions would automatically seek out the instrument if it’s vacant. They’d gain Dagger Main-hand as a new weapon.
They could also focus much less on subterfuge and more on direct conflict as a Duelist, gaining new Counter techniques in which the Mesmer blurs and readies a counter maneuver, be it an attack, stacking conditions or just moving out of the way, whenever the next enemy attacks. They gain Pistol main-hand and Shortbow as new weapons.