For one Kodak and two Olympus cameras there seem to be various settings possible, with either loss of information or without it. Maybe, even for cameras which are reported as black=0 here there is a setting which could produce darkframes with far from zero (ideally, even 1st percentil should be non-zero for 12-bit cameras).
AVT F-145C black=0
AVT F-201C black=0
AVT F-510C black=0
AVT F-810C black=0
Canon EOS 10D black=125
Canon EOS-1D black=0
Canon EOS-1D Mark II black=127
Canon EOS-1D Mark II N black=128
Canon EOS-1DS black=0
Canon EOS-1Ds Mark II black=128
Canon EOS 20D black=127
Canon EOS 300D DIGITAL black=120
Canon EOS 30D black=128
Canon EOS 350D DIGITAL black=256
Canon EOS 5D black=127
Canon EOS D2000C black=200
Canon EOS D30 black=126
Canon EOS D60 black=127
Canon EOS DIGITAL REBEL black=125
Canon EOS DIGITAL REBEL XT black=255
Canon EOS Kiss Digital black=122
Canon EOS Kiss Digital N black=257
Canon PowerShot 600 black=0
Canon PowerShot A50 black=30
Canon PowerShot A5 black=23
Canon PowerShot A5 Zoom black=23
Canon PowerShot G1 black=28
Canon PowerShot G2 black=32
Canon PowerShot G3 black=128
Canon PowerShot G5 black=126
Canon PowerShot G6 black=128
Canon PowerShot Pro1 black=129
Canon PowerShot Pro70 black=34
Canon PowerShot Pro90 IS black=31
Canon PowerShot S30 black=31
Canon PowerShot S40 black=32
Canon PowerShot S45 black=128
Canon PowerShot S50 black=129
Canon PowerShot S60 black=130
Canon PowerShot S70 black=129
CASIO EX-P505 black=0
CASIO EX-P600 black=0
CASIO EX-P700 black=0
CASIO EX-S100 black=0
CASIO EX-Z50 black=0
CASIO EX-Z55 black=0
CASIO QV-2000UX black=0
CASIO QV-3*00EX black=0
CASIO QV-4000 black=0
CASIO QV-5700 black=0
CASIO QV-R51 black=0
Contax N Digital black=0
Creative PC-CAM 600 black=0
EPSON R-D1 black=63
EPSON R-D1s black=62
Foculus 531C black=0
FUJIFILM FinePix E550 black=0
FUJIFILM FinePix E900 black=0
FUJIFILM FinePix F700 black=0
FUJIFILM FinePix F710 black=0
FUJIFILM FinePix S20Pro black=0
FUJIFILM FinePix S2Pro black=128
FUJIFILM FinePix S3Pro black=0
FUJIFILM FinePix S5000 black=0
FUJIFILM FinePix S5100 black=0
FUJIFILM FinePix S5200 black=0
FUJIFILM FinePix S5600 black=0
FUJIFILM FinePix S7000 black=0
FUJIFILM FinePix S9500 black=0
Imacon Ixpress 16-Mp black=0
Imacon Ixpress 22-Mp black=0
Imacon Ixpress 39-Mp black=0
ISG 2020x1520 black=0
Kodak DC120 black=0
Kodak DC20 black=0
Kodak DC25 black=0
Kodak DC40 black=0
Kodak DC50 black=0
Kodak DCS315C black=8
Kodak DCS330C black=8
KODAK DCS420 black=5
KODAK DCS460A black=8
KODAK DCS460 black=20
Kodak DCS520C black=169
Kodak DCS560C black=174
Kodak DCS620C black=185
Kodak DCS620X black=195
Kodak DCS660C black=174
Kodak DCS660M black=202
Kodak DCS720X black=0
Kodak DCS760C black=0
Kodak DCS760M black=0
Kodak DCS Pro 14N black=0
Kodak DCS Pro 14n black=0
Kodak DCS Pro 14nx black=0
Kodak DCS Pro SLR/c black=0
Kodak DCS Pro SLR/n black=0
KODAK EOSDCS1 black=6
KODAK EOSDCS3B black=0
Kodak KAI-0340 black=0
KODAK NC2000F black=0
KODAK NC2000G black=0, KODAK NC2000G black=3
KODAK P850 ZOOM black=0
KODAK P880 ZOOM black=0
Kodak ProBack645 black=0
Kodak ProBack black=0
Konica KD-400Z black=0
Konica KD-510Z black=0
Leaf 3024x1944 black=0
Leaf Aptus 17 black=0
Leaf Aptus 22 black=0
Leaf Aptus 65 black=0
Leaf Aptus 75 black=0
Leaf Cantare black=0
Leaf CatchLight black=0
Leaf CMost black=0
Leaf DCB2 black=0
Leaf Valeo 11 black=0
Leaf Valeo 17 black=0
Leaf Valeo 22 black=0
Leaf Valeo 6 black=0
Leaf Volare black=0
LEICA DIGILUX 2 black=0
LEICA D-LUX2 black=0
Logitech Fotoman Pixtura black=0
Micron 2010 black=110
MINOLTA ALPHA-7 DIGITAL black=0
Minolta DiMAGE 5 black=0
Minolta DiMAGE 7 black=0
Minolta DiMAGE 7Hi black=0
Minolta DiMAGE A1 black=0
MINOLTA DiMAGE A200 black=0
Minolta DiMAGE A2 black=0
MINOLTA DiMAGE G400 black=0
Minolta DiMAGE G500 black=0
MINOLTA DiMAGE G530 black=0
Minolta DiMAGE G600 black=0
Minolta DiMAGE Z2 black=0
MINOLTA DYNAX 5D black=0
MINOLTA DYNAX 7D black=0
Minolta RD175 black=0
NIKON D100 black=0
NIKON D1 black=0
NIKON D1H black=0
NIKON D1X black=0
NIKON D200 black=0
NIKON D2H black=0
NIKON D2Hs black=0
NIKON D2X black=0
NIKON D2Xs black=0
NIKON D50 black=0
NIKON D70 black=0
NIKON D70s black=0
NIKON D80 black=0
NIKON E2100 black=0
NIKON E2500 black=0
NIKON E3700 black=0
NIKON E4300 black=0
NIKON E4500 black=0
NIKON E5000 black=0
NIKON E5400 black=0
NIKON E5700 black=0
NIKON E800 black=0
NIKON E8400 black=0
NIKON E8700 black=0
NIKON E8800 black=0
NIKON E880 black=0
NIKON E900 black=0
NIKON E950 black=0
NIKON E990 black=0
NIKON E995 black=0
Nucore BMQ black=0
Nucore RAW black=0
OLYMPUS C3030Z black=0
OLYMPUS C5050Z black=0
OLYMPUS C5060WZ black=0
OLYMPUS C7070WZ black=0
OLYMPUS C70Z,C7000Z black=0
OLYMPUS C740UZ black=0
OLYMPUS C770UZ black=0
OLYMPUS C8080WZ black=0
OLYMPUS C860L,D360L black=0
OLYMPUS E-10 black=2048
OLYMPUS E-1 black=1024
OLYMPUS E-20,E-20N,E-20P black=2560
OLYMPUS E-300 black=0, OLYMPUS E-300 black=63
OLYMPUS E-330 black=0, OLYMPUS E-330 black=125, OLYMPUS E-330 black=82
OLYMPUS E-500 black=63
OLYMPUS SP350 black=0
OLYMPUS SP500UZ black=0
Panasonic DMC-FZ30 black=0
Panasonic DMC-LC1 black=0
Panasonic DMC-LX1 black=0
PENTAX *ist D black=127
PENTAX *ist DL black=127
PENTAX *ist DS black=128
PENTAX K100D black=127
PENTAX Optio 33WR black=0
PENTAX Optio S4 black=0
PENTAX Optio S4i black=0
PENTAX Optio S black=0
Phase One H 10 black=0
Phase One H 20 black=0
Phase One H 25 black=0
Phase One LightPhase black=0
Phase One P 20 black=0
Phase One P 25 black=0
Phase One P 30 black=0
Phase One P 45 black=0
Pixelink A782 black=0
Rollei d530flex black=0
RoverShot 3320AF black=0
SAMSUNG GX-1S black=127
Sarnoff 4096x5440 black=0
Sinar 3072x2048 black=0
Sinar 4080x4080 black=0
Sinar 4080x5440 black=0
Sinar Sinarback 54 M, Hasselblad black=0
SMaL v6 1288x1024 black=0
SMaL v6 643x482 black=0
SMaL v9 1284x864 black=0
SMaL v9 1288x864 black=0
SMaL v9 1632x1220 black=0
SMaL v9 2032x1520 black=0
SMaL v9 816x612 black=0
SONY DSC-F828 black=491
SONY DSC-R1 black=512
SONY DSC-V3 black=255
SONY DSLR-A100 black=0
Sony XCD-SX910CR black=0
ST Micro STV680 VGA black=16