Title says it all: what attack or combo do you find the most satisfying to do?
For me, it's using Devil Trigger, Angel Pulling myself towards an enemy, and using a fully charged Showdown with Eryx, dribbling them until they're dead. It's definitely my favorite way of killing those damn Dream Runners, especially in DMD when they send a pair of them your way, or add a Witch into the mix. I might not get much in the way of style for it, but man if it doesn't feel good to kill them quick!
"Even a stray has pride." -Gabranth, Final Fantasy XII PSN: Mysteltain
I like the Quick Trinity Smash. Rebellion, Rebellion, pause, switch to Arbiter, end the combo with the triple-hit Trinity Smash. It's especially effective if you use it following a Rebellion, Rebellion, pause, switch to Aquila, and pull in a bunch of guys.
Kind of long... But I like to Prop w/Osirus, Shredder, Launcher (hold) w/Rebellion, two hits, triangle move (arbiter), tremor to bring me back to the ground (O+Arbiter in the air), followed up by Drive, Overdrive.
If anything is left alive after that (rarely) I'll use the ophinion and do something small to kill them. Sometimes stinger/trillion stab.