Preston,
We've used pecan shells. They work just great. We tried them when we were out of wood, I had just shelled a bunch of pecans. We soaked them for a day, drained, then added them to the hot coals. Since then we've just thrown them on dry. Runs up the heat a bit but still get a nice flavor. I think if there is a little pecan meat in the shells still, it works like you had soaked them.
We used them with turkey, pork(not as good, but when you just want the smoke, it's great), even tried them with salmon(not a great taste).
Trimmings from your citrus trees are good to smoke with, too. We didn't even soak them, since they were green, but they were good with chicken.
I think they'd be great with fish too.
Peggy
2 Greyhounds....SMOKIN!!!!