My favourite build so far -- in terms of theme, roleplaying (character), roleplaying (party role) -- is a draconic bloodline (red) sorcerer. I don't just love it for the twinned haste, but all those glorious Walls of Fire, Fireballs, and Scorching Rays. The free Mage Armor also is pretty nice -- gives me one more use if Shield if I really need it. Draconic Flight is a little undercut by the Illithid Powers equivalent, but I think it's worth avoiding
the cosmetic damage and dealing with the Emperor.
I went 6/4/2 Draco Sorc/GOO Lock/Fighter for my first honour mode run, and it was quite powerful, but it lacked the distinct flavour of the monoclass sorcerer, imo.
One of my favorite characters so far is my elven red draco sorc, Aine, who I played as a NE criminal. I always had Astarion and Lae'Zel in my party, and usually Shadowheart. Helped Mol in the Druid's Grove with her little task, worked witih the Zhentarim, and was generally very forward about my expectations of material rewards -- and I always pursued more, given the chance. I even kept a dragon horde in camp -- a chest filled with all the metal ingots, precious gems, jewelry, silverware (note: actually silver), and precious metal cups and goblets that I had found. By the time I got to act 3, I had a horde worth nearly 10k gold.
In terms of mechanics, well... sending a few Fireballs into a group of enemies caught in Hunger of Hadar courtesy of your warlock friend is just *chef's kiss*
