Phase Shifter
Discrete transistors find there way into phase shifters in two ways. Most commonly, JFETs can be used as the variable resistance component. Less commonly, discrete transistors, typically BJTs can be used as the splitting/amplifying element. The few examples of pre-op amp phase shifter effects had to use discrete transistors. Really early versions used vacuum tubes for the active element and obsolete varistors as the variable resistors.
BJT used as the splitting/amplifying device, optocoupler variable resistor:
Uni Vibe
Matched JFET phase shifters:
Maestro Phase Shifter
MXR Phase 90
Electro Harmonix Bad Stone (early versions)
Not to be confused with phase shift oscillators, found under the oscillator page.