Unconventional density waves (UDW) are one of the ground states in metallic crystalline solids and have been speculated already in 1968. However, more focused studies on UDWstarted only recently, perhaps after the identification of the low temperature phase in α-(BEDT-TTF)2KHg(SCN)4 as unconventional charge density wave (UCDW) in 2002. More recently, the metallic phase of Bechgaard salts (TMTSF)2X with X=PF6 and ReO4 under both pressure and magnetic field appears to be unconventional spin density wave (USDW). The pseudogap regime of high Tc superconductors LSCO, YBCO, Bi2212 and the one in CeCoIn5 belong to d-wave density waves (d-DW). In these identifications, the angular dependent magnetoresistance and the giant Nernst effect have played the crucial role. These are the simplest manifestations of the Landau quantization of quasiparticle energy in UDW in the presence of magnetic field (the Nersesyan effect). Also we speculate that UDW will be most likely found in α-(BEDT-TTF)2I3, α-(BEDT-TTF)2I2Br, κ-(BEDT-TTF)2Cu(NCS)2, κ-(BEDT-TTF)2Cu(CN)2Br, γ-(BEDT)2GaCl4 and in many other organic compounds.