Not sure if these would count as spells.
Pinkie Sense is an ability Pinkie Pie has - a collection of weird twitches in various body parts that warn her of approaching events (most famously, twitchy tail means an imminent falling object) She has no control over it, but sometimes she gets a plot-relevant warning ahead.
Sonic Rainboom is Rainbow Dash's special move. Pegasi are normally capable of doing weird things, like walking on clouds or pulling chariots in the air, but if Dash flies fast enough to break the sound barrier, she creates a huge burst of rainbow colors and then, as long as she keeps the momentum she can pretty much disregard physics, no longer struggling against air resistance and doing 90 degree turns at mach one without as much as losing a feather. On one ocassion she used it to demolish Applejack's old barn, dive-bombing it and leaving a rainbow-colored mushroom cloud.
