Here's what I thought of so far:

Twilight -- Closes her eyes while her horn flares, and then opens them and spreads her wings.

Spike -- Concentrates hard and raises his claws toward the target.

Rainbow Dash -- Spins around in the air twice, spreading her forelegs wide.

Applejack -- Inhales while raising her upper body, then stomps down hard.

Pinkie Pie -- Makes a silly face while circling her hooves around and jumps in the air.

Rarity -- Spins around on her hind legs while her horn flares; she then poses with one hoof off the ground in a dramatic fashion.

Fluttershy -- Panics a little but then opens her eyes with confidence, arcing her hooves.

Very nice. I could imagine more down the line for guest party members.

Sunset -- Eyes closed; holds her hooves/hands close to her chest, and then opens her eyes and outstretches her front legs/arms .