For me it would be Zen.
1) I just don't like click pens in general, most mechanisms, even well made ones, still have a "cheap" feel to me and would have trouble selling them for any more than a "slimline" type
2)I recently turned a Zen for the first time, and I actually liked it quite a bit. Not bulky, but enough meat on it to show off the wood and give it a solid feel (10.5mm tube). Plus, the magnetic top is just "gimicky" and different enough to make them stand out a little more from some others, and the general fit and finish of the components themselves is a little higher than in most long clicks and seems to justify a slightly higher price tag on the finished product...
Just my opinion...