This brief overview summarizes the state-of-the-art of simulations of transition metal nanoclusters based on density functional theory calculations. Besides the monometallic clusters like iron, we focus on alloy nanoclusters like Fe-Pt, Co-Pt and (Ni, Co)-Mn-Ga which are of current interest for recording media and actuators involving the magnetic shape memory effect, respectively. Although catalysis is not the subject of the present paper, trimetallic nanoclusters are of special interest because the third element can be used to achieve higher catalytic and selective properties compared to the corresponding monometallic and bimetallic clusters. For clusters of Fe-Pt and Co-Pt below a critical size, the L12 structure with its technologically relevant high magnetocrystalline anisotropy, is difficult to stabilize. For trimetallic systems like Ni-Mn-Ga, the rather versatile properties of the bulk material can be used to achieve shape changes or magnetocaloric effects (depending on the composition) also in nanoclusters. More importantly, it might be cheaper to manufacture the nanocrystalline materials from the trimetallic nanoclusters than to fabricate corresponding single-crystal bulk systems.