I have been having a lot of fun with Devil Survivor 2 Record Breaker. There is a passive spell called money bags. I taught it to all eight of the demons in my party and now I have like, 30,000 macca. It's bullshit
I thought that Dragon Age had a really boring magic system, as much as I wanted to like that game. Planescape Torment had some interesting spells, there were even a few lore-focused ones like conjure spirit from Arcanum.
I always had a soft spot for the magic system in Runescape, too. Although I kind of spoiled the excitement of it for myself by looking stuff up on the wiki.
In terms of more original systems, as other sushis have mentioned Magicka had a neat system too, although I could never really get the hang of it. I wonder if they were inspired by the Invoker character from DotA.
I think Planescape Torment had the best magic I've ever played, and that's because I include all the random magical creatures, artifacts in the game as part of its "magic system". I really love the shop that sells bullshit magical artifacts, because there're several quests which solely consist of fetching random magical bullshit from that shop and using it to solve whatever bullshit magical problem has occured. And that shit with the wizard what curses that one dude to always smell bad no matter what and what also curses you to have hiccups forever? Very cool magics.