For me the brake lever I like and have a good performance are the Extralite Ultralevers. They are quite good: 32 gr and no flex, good performace even with disc brakes. I still use with BB7. I started to use long time ago with V brakes and they are quite nice.
The Kooka looks very nice but I don´t like how they perform. My hands are not big but they are unconfortable and not very powerfull.
Retro I like a lot the Odisey Paralevers yellow and black version:
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But the best design ... Shimano XT. They are perfect.