Prednisone
"I have severe allergies, combined with chronic sinus and ear troubles.  Every few months, I need prednisone to help with inflammation.  It kicks in so quickly, and that familiar, dull ache finally subsides.  With the taper pack, the side effects are minimal, but the most notable are an increased appetite and energy level.  Thankfully, the two of these together seem to balance out, and I usually don't gain weight."