Hm, tough question. I have little emotional attachment to my D40 - the first DSLR I used - but I still have it for backup and taking pictures of the D7000. =P I'm not sure about the D7000. I don't think I've had it long enough to know. My little 35 1.8 is pretty special to me, because it's fun to use and does everything I need it to.
That said, I'm still very new to photography, so maybe 10 or 20 years from now my answer will be different. =)
Really interesting to see people's comments here, BTW.