Mine? Profane Zealot. I don't know why, I just think the villain card looks damn good :P
Ablative Coating, Temporal Shielding, and Elemental Exochassis - because I created them with a kickstarter reward 
Rocket Punch - because it takes me back to my childhood, getting up early to watch Tranzor Z, and because I always say it like Captain Falcon from Smash Brothers every time I use it
Arcane Cadence - just due to sheer usefulness
I will re-visit this thread once Vengeance comes out. There's a few in there.
For mechanics, Twist the Ether, hands down the most shenanigan inducing card in the game.
Overall: Consider the Price of Victory, and Targetting Innocents. When I play the game I write the comic in my head of how it is happening. Those two cards really changed just how serious I viewed those matches. (Consider the Price is what prompted me to play Fanatic in reckless attack mode, so it holds a special place in my heart for helping me find my favorite hero)
here's a link to the original Savage Mana
http://greaterthangames.com/sites/default/files/forum/attachments/hero_haka_08_x2.png
Wow, that card would be broken. Since it says "Deal 1 Target 2 damage for each card" instead of "Deal 1 Target X damage where X = the amount of cards times 2" that means damage buffs would affect each card underneath Savage Mana.
If only…
yes, that's true, although enemy armor affected the card twice as much as well.
I think Lightspeed Barrage used to have the same issue.
@Envisioner
The cards in question are Haka of Shielding and one of the Trap cards, I don't remember which one. Ambuscade's card shows him planting a bomb on Haka at a zoo, and Haka's shows the effect of the bomb having very little effect.
Edit: The Haka of Shielding card's art was changed in EE, but it's the EE version that's being discussed.
Ambuscade's corresponding card is his Personal Cloaking Device
For some reason I thought there were at least 3 cards that showed it, but it was probably only the two previously mentioned. Either way, it still makes me laugh.
It is for that reason that I call the Haka of Shielding the Haka of Sandwich.
Also, I really like the Tumbleweed; my friends and I have deemed it the MOST IMPORTANT CHARACTER IN SENTINELS, and will announce it as such whenever it comes up.
Oh, I never said my favourite.
I have got to go with cmschex's choice of Inconceivable Obstruction, not only is it (to me) an excellent marriage of art, flavour text and mechanics but it also encompasses the comic book absurdity that Sentinels can affectionately mock while still showing its appreciation for the genre and simultaneously integrating it into the game on its own merits.
Also, it is inconceivable that you would choose something else.
You keep saying that word. I do not think it means what you think it means...
Jim's Hat, Electro Deployment Unit, HUD Goggles, The Legacy Ring, Utility Belt. I like to be able to DO MORE THINGS.
"AAAAAGH! Stop it!"
"But we're not quoting Monty Python!"
"THIS IS WORSE!!!"
I thought The Fancy Crew were the only ones who did that. Great minds think alike, I suppose.
Ha! I love it!
easy the first edition savage mana
Haka must save us from the hippocalypse!
... going to have to track down a set of those :)
Playing a game the other day with Time Cataclysm the Tumbleweed was the play immediately after End of Days obliterated a bunch of cards and made Iron Legacy very sad. So it even has a very good sense of timing!
The tumbleweed has primary target status in our group, it has never lasted a round, and usually the first player will kill it, often going overboard in doing so. It has never been retributioned, but it has drawn Haka of Battle and Lightspeed Barrage.