wow.. that's a hard one 
I've got a few that I'd definitely miss the most and they're high candidates..
holga 120 cfn with fortepan 100 or sx-70 sonar with artistic tz
but as much as I love them (and both films being goners) I have to pick something that I actually can see myself ditching everything else for; my yashica 635~ I'd pair it with some positive film, ektachrome something, so then I could process it as positive, black and white or go xpro.
I'd be very much satisfied with that 
...I just wish that yashica was a rolleiflex with 2.8 lens! haha~
Wow! quite the throwback seeing this
I really like my yashica 635 but I've realised that I have a quite soft example so I'd like something similar but with a sharper lens.
But now I'd rather say my Bronica C. maybe not as light as a TLR but it sure is a joy to use and I get lovely results from it. the 7,5 cm nikkor is a snug fit and bright enough with the 2.8 aperture. for film I guess I should say HP5, but maybe just because I've been shooting that a lot more recently (in medium format)
Say hello to Mr. Metal n Chrome by
jonas lundström, on Flickr
