Some I will watch again:

Adam and Steve
Angels in America
Another Country
Bad Education
Beautiful Thing
Brokeback Mountain
Far From Heaven
Heights (did anyone mention this)
I Think I do
Latter Days
Longtime Companion
The Lost Language of Cranes
Ludwig
Milk
My Beautiful Launderette
Parting Glances
Presque Rien
Shelter
The Talented Mr Ripley
Trick

Maybe not all 'gay' movies, but certainly those that are not always categorised as such have gay cores.