  In the context of the gauge coupling unification, we present a comprehensive
analysis of the extensions of the Standard Model with vector-like fermions and
scalars. We find 145 models that satisfy the unification condition, which are
distinguishable by the number of new particles in the spectrum and by their
transformation properties under the gauge symmetry group of the Standard Model.
For all models we derive lower bounds on the exotic fermion and scalar masses,
stemming from the measurement of the strong gauge coupling scale dependence,
from the heavy stable charged particle searches, and from the electroweak
precision tests. We also discuss the potential of testing the unification
scenarios at the future 100 TeV collider and in the proton decay experiments.
We show that many models can already be excluded based on the current data,
while many others will be entirely probed in the coming years.
