It is well established that CD8⁺ T cells constitute an important branch of adaptive immunity contributing to clearance of intracellular pathogens and providing long-term protection. These functions are mostly fulfilled by the best characterized subpopulation of CD8⁺ T cells, the cytotoxic T lymphocytes (also called Tc1 cells), owing to their ability to kill infected cells and to secrete cytokines such as interferon-γ and tumor necrosis factor-α. However, there is growing evidence for alternative CD8⁺ T cell fates influencing CD4⁺ T-cell-mediated responses in the context of allergy, autoimmunity and infections. Thus, like subpopulations of CD4⁺ T cells, also CD8⁺ T cells under particular conditions acquire the expression of interleukin (IL)-4, IL-5, IL-9, IL-13, IL-17 or suppressive activity and thereby influence immune responses. The process of CD8⁺ T-cell differentiation is dictated by antigen strength, co-stimulatory molecules and cytokines. These environmental cues induce transcription factors further specifying CD8⁺ T-cell decision into Tc1, Tc2, Tc9, Tc17 or CD8⁺ T regulatory fate. Here, we discuss our current understanding about functional diversity of effector CD8⁺ T cells and contribution of transcription factors to this process.