Luke, sounds like a coke-bottle shape is winning the vote so far. I am a fan of them too but I especially like them when it's a more compound shape. eg/ a different profile looking top down versus a side view. I just drew a 30 second sketch (meaning very rough) that shows what I mean more clearly than any explanation I can try to give will. of the the three images, the top one is the top down view. Pretty classic coke bottle with a taper near the ferrule and the recess across the middle. Those always feel good in a pinch grip and have a nice balance to them.
The second sketch is the side profile... it's slightly higher than the spine in the middle but otherwise only has a slight curve along the top edge. The bottom, more ergonomically, has extra belly in the middle. I like these with an angled end - partly to shave weight and help keep a neutral balance on the knife, and partly just because I think they look cool. If the the angle of the end of the handle is parallel to the choil, think it gives a great look. One exception - end caps on an angled handle heel tend to throw me off a little. I like symmetry in the angles for different handle components. If spacers, a ferrule, end cap etc have different angles/lines to them at the joints it tends to make the handle stand out more than the blade - at least to my eye. If an end cap is involved, I like a flatter end similar to the third sketch.
As particular as that is, though, don't think there's any wrong answer if a handle feels good in the hand. I'm looking forward to seeing what you guys come up with.
-seth