I myself have a few mods including the Screw Driver. However, if you are looking for something that is different from the 901, produces huge vapor and doesn't look funny in public, I would highly suggest the manual Joye510. It produces more vapor and throat hit than any of my mods. I loved it so much from the beginning, I have no purchased 7 kits, 25 extra atomizers, and 12 extra batteries.
I would suggest a mod like the GG or SD for someone who does not mind looking funny in public or does not plan on using it in public.
EDIT: Sorry, I didn't see Feathersncream's recommendation! Great minds think alike.