I've updated and added a number of experience awards. I've removed all "best character" awards that only a single character could earn and replaced them with general versions that multiple characters can earn. I've also tried to fill in some gaps for support and defender roles. The full list of awards below.
ASSISTED KILL
This award is given to each player character that dealt damage to an enemy during the encounter but did not defeat that enemy.
DEAD WHISPER
This award is given to each player character that uses a healing power to allow a dying or unconscious ally to heal herself.
DOUBLE KILL
This award is given to each player character that defeats two or more enemies in a single turn during the encounter.
DOUBLE TEAM
This award is given to each player character that grants an ally flanking for an attack during the encounter.
EXHAUSTED
This award is given to each player character that has exhausted all of her encounter and daily attack powers by the end of the encounter.
FIRST TO ACT
This award is given to each player character that takes any action during the surprise round of the encounter.
FIRST BLOOD
This award is given to each player character that bloodies a non-minion enemy during the encounter.
FLAWLESS
This award is given to each player character that completes the encounter without taking damage.
GOT YOUR BACK
This award is given to each player character that uses a power to grant an ally any bonus during the encounter.
HEAD SHOT
This award is given to each player character that deals critical damage to an enemy during the encounter.
IMPROVISED KILL
This award is given to each player character that bloodies or reduces an enemy to 0 hit points with an improvised weapon or a weapon she isn't trained with during the encounter.
IN THE FRAY
This award is given to each player character that started or ended her turn threatening an enemy during every round of the encounter.
KILL STEAL
This award is given to each player character that reduces a non-minion enemy with less than maximum hit points she has not previously dealt damage to to 0 hit points during the encounter.
KNOWLEDGEABLE
This award is given to each player character that used a knowledge skill to learn some useful information about an enemy, trap or hazard during the encounter.
LET IT BURN
This award is given to each player character that reduces an enemy to 0 hit points with ongoing damage during the encounter.
MATCH POINT
This award is given to each player character that reduces an elite or solo enemy to 0 hit points during the encounter.
MEDICINE MAN
This award is given to each player character that uses a healing power to allow an ally to heal herself.
OBSERVERANT
This award is given to each player character that notices a hidden or invisible creature or discerns an illusion or bluff during the encounter.
ONE HIT K.O.
This award is given to each player character that defeats an unharmed non-minion enemy with a single attack.
OUTSIDER
This award is given to each player character that doesn't begin or end any turn adjacent to an enemy during the encounter.
OVERKILL
This award is given to each player character that dealt more than half of a non-minion creature's maximum hit points in damage to that creature with a single attack.
PUNCHING BAG
This award is given to each player character that is bloodied during the encounter.
READY FOR ACTION
This award is given to each player character that prepared a readied action and had that readied action triggered during the encounter.
RISEN ANEW
This award is given to each player character that is reduced to 0 hit points during the encounter but ends the encounter with 1 or more hit points.
RUNNING MAN
This award is given to each player character that moves at least thirty meters during the encounter.
SECOND WIND
This award is given to each player character that is bloodied during the encounter but ends the encounter with hit points greater than its bloodied value.
SURPRISE K.O.
This award is given to each player character that dropped a non-minion enemy during the surprise round or during the first round of the encounter.
TAKE UM DOWN
This award is given to each player character that uses a power to inflict any negative condition or penalty on an enemy during the encounter.
UNLUCKY
This award is given to each player character that rolled a natural 1 on a d20 roll during the encounter.
UNMOVING
This award is given to each player character that doesn't leave her starting space during the encounter.
Discuss below and make suggestions for other awards.
