In this talk we present two simple but complete genuinely multidimensional Riemann solvers for nonlinear systems of hyperbolic conservation laws on general unstructured polygonal Voronoi-like tessellations. The first method is a direct extension of the Osher-Solomon Riemann solver to multiple space dimensions. Here, the multi-dimensional numerical dissipation is obtained by integrating the absolute value of the flux Jacobians over a dual triangular mesh around each node of the primal Voronoi mesh. The second method is a multidimensional upwind flux based on the so-called $N$-scheme, originally developed in the framework of residual distribution (RD). Both methods use the full eigenstructure of the underlying hyperbolic system and are therefore complete by construction. Then, a simple higher order extension up to fourth order in space and time is introduced at the aid of a CWENO reconstruction in space and an ADER approach in time, leading to a family of high order accurate fully-discrete one-step schemes based on genuinely multidimensional Riemann solvers. We close the talk by showing applications of our new numerical schemes to several test problems in the field of the compressible Euler equations. In particular, we show that the proposed schemes are at the same time carbuncle-free and preserve certain stationary shear waves exactly.