I've been thinking of an answer for this question for awhile.
I always liked the "muddler minnow" for an all around fly as I can fish it wet or dry and it works well for any trout.
A twister tail type rubber jig is a pretty good all around pike/walleye lure.
I was going to choose a spoon of some sort for #3 but got to thinking about ice fishing and I like a swedish jig for an all around ice fishing lure.
However a "pickerel rig" with worm for bait is something that (when legal) can be used anywhere, anytime for any fish.