Personally, I think trying to make something "Cool" for the sake of it being "cool" often backfires. Watch any Michael Bay movie to understand what I mean.
I'm going to gripe about magic in fantasy here: All too often, it seems to me, that writers use a spell or magical object solely for the purpose of being either a MacGuffin or a Deus Ex Machina. Harry Potter was really bad about this, IMO. Don't get me wrong, I loved those books, but all too often it seemed like a spell/potion/magical device had been invented for the sole purpose of writing the characters out of a jam. Maybe it works for some folks, but I didn't always buy it.
To avoid this, what I've done with my work was to make a rigid set of rules by which magic works. A bit like an RPG but much more freeform as there are no balancing or numbers to work around. Each magic-using character has a set number of spells to use, and then I worked their abilities into the story when they were useful.