I sell on Etsy, so my customers don't get to try them out first. The ones that sell the best are the Jrs, the PSI classic rollerball, and the cigars. Not that I've sold a lot at this point. As for people requesting pens locally, like coworkers, the most frequent request is the .30 cal bolt action just because they look cool. I'm not sure they care that much about the ink, but I always include the Schmidt Easy Flow 9000 in them.
On a personal note, I do like a rollerball, and very frequently carry one, but I do not like the balance (lack of) when the cap is posted. Way too top heavy. The lesser tip extension of a Pilot G2 on my Jr Milton bothers me so I stuck with the kit fill and, so far, I have not needed to refill it. My other personal carries are a cigar and a Duraclick EDC (the lighter weight aluminum variety). I like the balance of both and use the Schmidt. I don't think you can really go wrong with a nice cigar pen for overall feel.
Around the house, I have several Compsons hanging around (mostly because I screwed them up while pressing - don't get me started on that topic) and I really like them as far as general use. They are very well balanced, it's an easy one hand click operation, and there's no caps to keep an eye on. The gel ink that comes with them is really pretty smooth, but doesn't last long. That gets replaced with the Schmidt also.
Ultimately, I advise people to buy a pen they will realistically use, not just something to decorate their desk or pocket.