Best movie you love, not many people have seen.

A few stick out from going by the low votes method but I'm sure some of these are simple old enough that they never caught on for the IMDb crowd...

The Razor's Edge (1984)
Little Forest (2018)
Fandango (1985)
A Raisin in the Sun (1961)

Time travel features highly on this thread let me add another from Japan that's a lot of fun;

Beyond the Infinite Two Minutes (2020) original title Dorosute no hate de bokura

I sorted a list of my favorites off LetterboxD by lowest lifetime popularity and here are a bunch. I omitted films others have mentioned.

Islands in the Stream (1977)
Hunters Blood (1986)
Women’s Prison Massacre (1983)
The Last Hunter (1980)
Firecracker (1981)
The Survivors (1983)
Eugenie de Sade (1973)
The Challenge (1982)
Killer Fish (1979)
Man From Deep River (1972)
Street Law (1974)
Massacre Mafia Style (1974)
The Big Racket (1976)
Hands of Steel (1986)
The Wild Geese (1978)
Death Smiles on a Murderer (1973)
Raiders of Atlantis (1983)
And God Said to Cain (1970)
Hitch Hike (1977)

My favourite film - Dial M For Murder (1954).

Also The Skeleton Key (2005)