Originally Posted by arevan

4.
Not exactly *way* off the beaten path, but one that sees quite few tourists is the Toden Arakawa line, the last (?) remaining tram line in Tokyo. It runs through some older, more traditional working-class neighbourhoods (so called "shitamachi").
Buy a day pass at one of the stations (400 yen). In doing so they'll know you're a tourist and give you a map showing some sights where you can make stops and walk around. Shows a different Tokyo compared to busy places like Shinjuku/Shibuya.

For a huge contrast between new and old Tokyo, go to Tsukishima (man made island in Tokyo bay). This place is definitely not a secret, but go there for a stroll along the shore an early evening and there won't be many tourists there. This is a good place to try the aforementioned monjayaki too.