Staple features of most theories:

Sherriff McAllister Theories: Xander Berkley is awesome. Rock, Paper, Scissors emphasis. Overanalysis of relationship with Patrick, which could apply to any suspect.

Bret Stiles Theories: Malcolm McDowell is awesome.

Ray Haffner Theories: He fits the physical description. Usually use their theories to judge other suspect's personalities. The most common suspect in process of elimination theories.

Bob Kirkland theories: Conveniently leave out plotholes.

Michael Kirkland theories: Don't explain why Jason Lennon doesn't recognise him.

Gale Bertram theories: They're alright. He doesn't fit the physical description. Closer to the reveal, he is being picked as a result of process of elimination.

Brett Partridge theories: Managed to counter-argue every argument against their theories, the most common of which is "Brett Partridge is dead."... I don't know if Brett Partridge fans are all lawyers, but I have nothing to say against them.