Here are some thoughts on the effects and guitar parts used for "Night Fever" by the Bee Gees:

Based on the recording, it seems like the main guitar parts likely utilize a combination of the following effects:

Wah-wah pedal - This is commonly used to create the signature "talking" guitar sound, sweeping through the frequency range.
Chorus/Flanger - These modulation effects can help thicken the guitar tone and create a shimmering, swooshing quality.
Overdrive/Distortion - Some light overdrive or distortion likely helps drive the guitar sound and make it stand out.
The guitar parts may be split between: slope

One guitar playing the main chord changes and rhythmic parts
Another guitar (or guitars) providing the more effects-drenched lead lines and melodic accents
The interplay between the rhythm and lead guitar parts helps create the full, dynamic sound of the song.