Woot:
Sly Flourish - For our group's rogue, it outdamages his encounter and some daily powers.
Witchfire - That attack penalty has, among other things, saved almost the whole party from being hit by a dragon's breath weapon twice: hit by witchfire, breath weapon, would have hit 3 party members but missed due to witchfire, was taken to bloodied, used breath weapon again, missed everyone, some by 2 or 3. We have 3 strikers in our group so a -4 or whatever it is for a round is significant since most BBEGs rarely live more than two or three rounds anyway.
Ranger slide-when-hit utility power(I forget its name) - This saved my ranger once or twice, like when he had 6 cultists(non-minion) around him, most flanking, ready to lay the smack down. First one hit, slipped out of the group, and the last 5 didn't even get to attack.
Flames of Phlegethos - mostly due to the fact that our warlock has critted with it 2/3 of the time he's used it. Damage around 45-55 + 5 ongoing at 2nd-3rd level.
Flaming Sphere - Attacks + auto damage + area denial? Yes please. Whenever our pre-campaign playtest wizard busted this out, the battle became a piece of cake.
Sacred Flame - radiant damage + vs ref + extra save for someone = greatness.
Divine Glow - Cleric 1st level AoE + buff? Winner.
Dragonborn Breath Weapon - most useful racial I've seen in play.
Elven Accuracy - I don't think I've ever not hit with both my Two-Fanged Strike attacks thanks to this power. Almost as useful as Dragon Breath.
Gummy-beary Juice - I don't remember its actual name, since this is what we call it, but the rogue 2nd level utility jump-delimiter. Adds 3-6 squares of movement per move - that ignores some difficult terrain - to our rogue's capabilities. Mobility++.
Meh:
Disruptive strike - Neat, but has had limited effect since the few times I've used it, the DM has either critted or rolled utter crap anyway(4 or less).
Priest's Shield - Seems kinda useful, but our cleric seems to rarely have an ally next to him, his strength is mediocre to have high Wis and Cha, and warlock sucks all the luck out of our cleric(warlock seems to never miss, cleric seems to never hit).
Rogue level 1 encounter powers - The fact that our rogue has simply not used his in several encounters says enough.
Raven Queen's Blessing - This one depends on party composition and cleric "DPS." In our balanced pre-test group, it rocked, "proccing" in nearly every battle, especially when combined with divine glow and minions. In our 1 cleric, 3 striker group, he's only been able to activate it once since he got it...
Eladrin Teleport - Occasionally very useful, mostly not even used in our pre-test.
Bleh:
Any ranger at-will that isn't Twin-Strike - I think my ranger has used my other power(don't even remember its name) twice in 4 levels...
Cleric 1st-level daily Guardian Thingy(whose name I forget) - It adds a bit of battlefield control, but in the few battles it was used before our cleric replaced it with the awesome Beacon of Hope, the enemies just moved around it.