A fetish was a strong, usually sexual, affinity for something.
Bernice Summerfield believed Ovmakh had a fetish for military hardware, which she collected. (PROSE: Mentioning the War)
The Tenth Doctor, upon observing that Slabs were made up of solid leather all the way through, jokingly said that "somebody has got one hell of a fetish". (TV: Smith and Jones)
Ianto Jones believed some fetishes should be kept private, such as fetishes for offices. (TV: Kiss Kiss, Bang Bang)
While talking to Toshiko Sato about how close she had become to Tommy Brockless, Owen Harper reassured Tosh that he didn't think she had some "weird fetish for defrosted men". (TV: To the Last Man)
As Torchwood Three investigated a series of murders, Jack Harkness reminded his comrades that they were dealing with a conspiracy, and not "a freak with some needle fetish". (TV: Reset)
Ram Singh believed Matteusz Andrzejewski was into Charlie Smith because he had a "weird sexual fetish" for aliens. (TV: Detained)
Chat told Jack Chance, who had disguised both her and himself as Veltrochni, that she hoped that it wasn't going to be another new fetish for him. (PROSE: Mission: Impractical)