The Penrose process governing extraction of energy from black holes by the simple effects related to uncharged or charged particles is discussed in most of the known variants related to Kerr black holes and Kerr naked singularities, or to electrically charged static black holes. Attention is focused on the magnetic Penrose process in its extremely efficient version enabling extreme acceleration of charged particles after ionization of uncharged matter, giving explanation of the ultra-high energy cosmic rays. The effect of radiative self-force of accelerated particles is briefly discussed. It is shown that in the ergosphere of Kerr black holes it could lead to a new verion of radiative Penrose process due to radiation of photons with negative energy as related to distant static observers that cause the extraction of black hole rotational energy in this version of the Penrose process.