If weather/terrain combos become a thing this gen (which it very well could, especially in VGC), this thing can clean pretty well with Rain/Electric Terrain boosted Thunder. Also, great Doubles utility moves with Fake Out, Speed Swap, Encore, and Wish. Not to mention it can set-up Electric Terrain on its own, essentially giving it +2 Speed and a +1 to one of its STABs, which could be a decent move to consider even in lower-tier singles, if it lands there.
Luckily, it actually benefits from all the terrains in some way. Electric is obvious. Psychic boosts a different one of its STABs, and with 110 Base Speed it definitely appreciates the blocked priority, especially Shadow Sneak. Grassy basically relieves one of its weaknesses in Ground (considering 90% of offensive Ground moves are EQ). Not much to be gained from Fairy, but not much to lose either. I think terrain versatility is going to be very important this gen, and Raichu really does well in all of them.