Ron, clearly.
Kevin, characterized as such by the prostitute and Jules.
Billy, I could easily see as bisexual.
Howie, repressed?
Kirby, living with Kevin, maybe channeling his obsession with Dale.
Dale, living with a homely woman. Possible.
Mr. Kim, not sure
Alec, nah.
Kirby's Boss, uses baseball bat as a phallic symbol. Doesn't have the heart to fire Kirby.
Billy's old frat: Loves touch football. Not a female in sight.