Favorite energy type? That's....weird. Do people have favorite energy types?
I guess "force" might be my answer. Non-elementally typed damage. So, what Magic Missile does, say. It bypasses most basic damage reduction (or did in previous editions? 5th does interesting things with resistances, I think. Though we've only seen a little of that so far), it doesn't leave you stuck with only fire spells to fight the red dragon, etc.
That said, I have seen electricity damage put to amazing use. "Touch of the Eel" was a spell our wizard would cast on me in the Temple game; the next enemy struck would then take my weapon damage plus the spell damage. At one point I literally exploded a 4 armed gorilla (I forget what they're called) when I walked into a room and rolled a 20 on that trusty purple die while Touch of the Eel was cast on me. Then there are the majestic lightning bolts I've seen cast (and have, on occasion, cast myself).
