Crocs or the nock offs+1
Bulk isn't a problem just hang them on the back somewhere with a carabiner.
A few key requirements for me are:
1. Must be easy to just step into when leaving the tent.
2. Must double as shower shoes.
3. Must be OK for walking a few miles.
4. Must be light weight.
Crocs meet all of those requirements nicely, but If I will be hiking a lot I might consider adding a pair of trail running shoes. Most trips I do not find that necessary, since my hikes while on tour are typically just short walks. That said when we spend a week in Yosemite Valley I bought a pair of light trail running shoes.
BTW, I own a pair of Vibram Five Fingers and enjoy running in them, but they do not meet requirement #1 since they are a pain to put on. Also they are not optimum as shower shoes (item #2). They are fine for hiking though.