If you're hitting up the Skytree, you'd be crazy to miss the Pokémon Center right next door - especially if you've got any Pokémon fans in your group. It's not just another gift shop; this place is basically Pokémon heaven, packed with merchandise you won't find anywhere else.
The location is super convenient since you're already there for the Skytree (right by Oshiage Station), so you're not going out of your way at all. And unlike some Tokyo attractions where you're rushed through, you can actually take your time here browsing all the exclusive stuff.