Tom would've stayed! I accidentally let him move away and I've missed him ever since. He was the first villager who gave me his picture, though, so at least I still have that to remember him by. ^^
Zell. Only Zell. Dumbest mistake I've made in New Leaf :'c </3. I'm so close to finally being able to get him again. I did lose count of my cycle though.
All of my move outs have been deliberate... but if I had to choose one villager to stay I would have kept Freya, I think. I do miss her but she's gone to a great home now :3 I just needed to make room for Lucky and she was my oldest villager so I thought it was right she move on. I did have her picture in the end as well so I guess that helped the move out. Do miss her though :3