Slim model numbers that are ok (remembering slim ecigs have short battery life, and I highly recommend manual batteries)
Joye 510, Joye 510 mega xl, KR808D-1, DSE901, DSE801
Most popular fat battery long charge models: Joye Ego, Riva 510 (or Riva 901 for 901 users)
Popular variable voltage mod: Provari (but there are lots and lots of mods - mods are ecigs that contain aa-ish size industrial strength batteries which are removed just like a flashlight's battery is removed, and charged in a separate charger)