Free observation deck on the 26th floor of the oddly named “Carrot Tower” building near the station. This is one of the city’s lesser known treasures, in my opinion. The northern side of the tower looks out onto both Shibuya and Tokyo Tower (Skytree can also be seen in the far distance), while from the south side you can see Mount Fuji on a clear day. The north side also has a restaurant (Sky Carrot) with many tables next to the window and the menu, judging from a brief glance, didn’t seem too expensive given the what you could pay for similar views in the likes of Roppongi Hills or Caretta Shiodome. The night views facing south are admittedly less impressive as Mount Fuji is covered in darkness leaving you only the low residential blocks of Setagaya on which to peer down. It does have a bar which is open until 10pm everyday, however (¥750 for a beer).
The good news for photographers is that you’re entirely free to bring tripods and the housed ventilation units before the glass provider ample space to set up for your shot. And if you make your way to the observation deck on a weekday evening, you should more or less have the place to yourself.