[xz18r]

I have a 600 and 800 mechanical pencil. Love them, the feel can’t be beat - only by the (significantly cheaper) Pentel Graphgear 1000.

[prpl]

Graphgear 500 is also excellent, though without a retractable tip. I think those who like the grip of a rotring would prefer it over the 1000.

[bobek]

Love Pentel Graphear 1000, have multiple distributed throughout the house/workshop and backpacks :)

The other I really like is UNI Kuru Toga, the plastic one (shrug). The twist mechanism actually works; it is slightly wider thus more comfortable (for me) for longer writing sessions.

[ykonstant]

The twist mechanism really does work, but unfortunately it is easy to damage (for me). I damaged two kuru togas in the span of 6 months, very frustrating. The twist still works, but it is very wonky.

[elromulous]

Love the rotring pencils.

If you haven't already, give the Alvin Draft/Matic a try, imho it's up there along with them.