For me, the best is Energy Overload, having a 3rd bar, and recovering Magicka from tapattacks is unbeatable.
My favorite Weapon Ulti (Hey, we get 2!) is Ballista. I'm just going to leave this here to Burst, and do something else... I soloed the Frost Monarch (Dropped another Belt of Air, but at least this one's Purple!) with a Dodge-roll (Hasty Retreat!) and Shielded Charge to play Burst Tank. Would've thought it would take longer, based on the other Atronach Monarch fights, but at least this one didn't have Lava to work around. Couldn't have done it without my pocket DPS, came right back up right after that fight. Is it me, or is it a little cheap (okay with Power Stone, but still! No Heroic Slash or nothin!) Didn't even need Dark Deal, it was over so fast.
I used to use EOL as my Boss Bar, now I don't have to!
So, what's your picks? Seeing as we can have 2, there's no reason not to pick 2. And why?