The SF Titan would be most accurately what you are looking for.
The older versions of the VB-16 (the CPF special still on sale in the Dealer or Custom/Mods B/S/T forum (lost it after the change to the new server) dim up and down (with memory of where you were) very, VERY low. Later versions don't dim nearly as low.
The Gatlight also does it, but I have not seen it myself. Nor have I seen the Titan I suppose, but the Titan has been described in great detail.
The LRI Photon Proton starts VERY low for red, and goes low (starting from high) in white, but not as low in white as the red starts.
The Gladius UI is nice (with level memory like the VB-16) and it dims kind of low, but not seriously low. Lower than the later VB-16's, but not as low as any of the others listed here.
Photon Freedom coin cell lights work like the Proton, but all in white (up and down are both white (or whatever color you buy)) and dim very very low.
The HDS EDC Ultimates can be SET so that a level is very low, but will still have four discreet levels unless you are in the settings menu. The new Novatac is supposed to have a slightly more accessible dimming menu (unconfirmed).