Studies of non-equilibrium fluctuations have held a center stage during the past few decades of the development of non-equilibrium statistical mechanics. Indeed, macroscopic fluctuations are supposed to display some universal behaviour, regardless of the precise microscopic dynamics of the process under study. In this talk, we shall consider a few examples of non-equilibrium fluctuations: the particle current in an interacting particle system, the diffusion of a tracer in a one-dimensional gas of particles with excluded mutual passage and the melting of an Ising quadrant. These different problems will be analyzed quantitatively with the help of the macroscopic fluctuation theory.