That's a tough question. It really depends on how big your minibog is going to be, if you're going to embed it into the ground a bit, etc.

Off the top of my head:

Cobra Lily -- I have heard this can survive down to -20C, well below freezing and way beyond what you'll see in Zone 6.
Just about any American Pitcher Plant except S. oreophila but S. purpurea in particular (S. purpurea grows in Canada)
D. filiformis (any variety except "Florida all red", which does not go dormant)
D. intermedia \
D. anglica ---- These 3 grow in Canada, Europe, etc. Idaho, where I live, is mostly zones 4 to 6, and all 3 of these grow outdoors here.
D. rotundifolia /
Dionaea muscipula (Venus Flytrap)

I currently have a 12" pot of 3 S. leucophylla (2 typical and 1 'Judith Hindle' hybrid) that appear to be surviving just fine, as well as a 6" pot of S. purpurea, and a 4" pot of S. purpurea ssp venosa (I believe). They appear to be doing just fine, and aren't loosing too much color. I won't know for sure until next spring. I am in Twin Falls, ID, zone 5 or 6 depending on who you ask.

I did have 2 pots of VFT but I did not winterize them at all and they did kick the bucket -- one was hurting before I put it out, another just froze solid due to the extremely tiny pot size. I have every intention of trying again later this year with a bigger, more winter-ready, pot.

I have purchased a few styrofoam insulated pots from Flytrapranch to see if that helps.