For me, the ones that have the "cool" factor in that I find them interesting in how they work and the fact that they're great cameras are the Zeiss Ikon Tenax II, the Werra 3, the Ducati (Sogno) and the Konica II.

But I'm also a fan of the lever-wind Retina IIa and the IIIC (Big C), as well Agfa Super Solinette, the Zeiss Ikon folding Contessa and Contina II, the Nettax and Super Nettel and the various Super Ikontas.

My favorite camera is the Zeiss Ikon Contax IIa.