Celerity

Must have for immobile mages. All the AP in the world won't help you if you can't catch them to cast.

Unsealed spellbook for ghost/tp and predator for obvious reasons are also severely underrated.

Is extra movespeed ever that bad though? I take it on most champions I take sorcery on purely for positioning and kiting purposes.

it is actually REALLY good for junglers. Keep in mind you can combine it with other movement speed runes to increase your damage output (PRedator, Stormraiders surge, river walking, relentless hunter)

You take it for the MS, not the damage. The damage is just the sprinkles on the cake that is your extra MS.

A P

R A M M U S?

I really like pairing it with Waterwalking when I'm playing a roaming mid, or someone that needs to wiggle their way in before dropping a gap closer/Electrocute burst - like Nidalee. Honestly the damage buff is weak sauce, but the movement speed helps out a lot if you build to complement it. See also: Jhin.

Is it ever not worth taking? It gives a huge speed boost to roaming midlaners, to the point of needing to be nerfed by 25%.