These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
YMMV: The Watcher
Foe Yay - A large portion of the movie. David constantly tries to get Joel to realize that they "need each other," and that their cat and mouse games are crucial to both of them.
Ho Yay - This movie has this in spades. All one-sided on David's part towards Joel.
Mind Game Ship - The pairing of David and Joel. Also canon in the movie.
Narm - Oh, several. The slow-motion shot of Reeves dancing headbanger-style to a Rob Zombie song while taunting a victim in an abandoned warehouse for one. And the fact that Joel had to take notes and write down that David was "watching me," as if he wouldn't be able to remember that if he didn't get it down on paper. One reviewer mentioned the scene where Joel's ex-lover was tied to the chair in the burning house, calling his name repeatedly in slow motion, and likened it to a spoof where Cartman from South Park acted the same. Only... they were serious here.
Yaoi Fangirl - In all seriousness, the only people that openly show that they like this movie appear to be these. Most (if not all) of the fan videos for this movie are dedications to David x Joel.