The paper describes theoretical models of plastic deformation based upon a conception of nanoscale ideal shear serving as an alternative to the standard mechanism of lattice dislocation nucleation. A model of new physical mechanism of plastic flow in fcc nanowires through nucleation and evolution of sub-surface nanodisturbances is considered. Also the effect of sub-surface nanodisturbances on deformation nanotwins generation is investigated. The model of lattice and grain-boundary dislocation emission from pores in nanocrystalline materials via nanoscale ideal shear under the action of realistically achievable stresses is proposed.