I've been doing this for a while now, as a way to get my players to try things outside their comfort zone, or to do things they didn't know they could do. For some of them its a big motivator, and some of them don't care. I've just been giving experience for completion. The special boon things are cool, but I'm worried about people having too much stuff to remember (they already do!). Maybe if I made achievement "sets" which, when all sub-achievements are completed, would grant the character an AP boon or something.
I got this list off of the rpg reddit some months back, added some of my own, and subtracted a few. (the amount in brackets is experience gained)
Martial (Heroic Tier)
Kill a foe over 10 squares away. [50]
Kill a foe in a surprise round. [50]
Kill a foe with a single blow (not a minion). [50]
Gain combat advantage by feinting (Bluff). [100]
Divine (Heroic Tier)
Heal a dying ally. [100]
Kill two undead with a single attack. [50]
Arcane (Heroic Tier)
Kill four foes with a burst spell. [50]
Kill a foe by targeting his weakest defense. [50]
Any (Heroic Tier)
Discover a secret door. [75]
Disable a trap. [75]
Kill a foe with a critical hit. [50]
Kill a foe with an attack made by using an action point. [50]
Use a knowledge skill to determine a enemy's powers. [75]
Use Acrobatics to perform a stunt or reduce falling damage. [75]
Use Athletics to Climb a cliff, Jump a pit, or Jump up to a ledge. [75]
Use Intimidate to force a bloodied target to surrender. [50]
Make an attack from hiding. [75]
Learn a dirty secret about a NPC and use it against them (Streetwise). [75]
Use something in your adventurers kit during an encounter. [100]
Push an enemy into something damaging. [75]
Delay your action to set up combat advantage. [75]
Kill an enemy by using a stunt. [100]
Party (Heroic Tier)
Achieve two milestones in a single "day" (without taking a long rest). [100]
Kill a monster 5 levels above the average party level. [50]
Successfully complete a skill challenge. [50]
Defeat a foe without using violence (trickery, diplomacy, etc.). [100]
Complete an encounter without using any At-Will powers. [100]
EDIT: Here's the
link to the thread on reddit.