Stimulator, sizes 8-18. Of all the so-called "searching" patterns, Stimulators are easily the most versatile. Small ones easily pass for caddisflies or small stoneflies; larger ones imitate big stoneflies or grasshoppers. I prefer them in their yellow, olive, brown, and Royal variations.
Elk-Hair Caddis, sizes 10-20. Until Al Troth introduced this high-floating, durable pattern, caddis imitations were too delicate and too hard to see. With their buggy silhouettes and generically shaped wings, Elk-Hairs provide a passable imitation for just about every down-winged insect a trout might eat. Tan, olive, and brown are the most effective colors.
Royal Wulff, sizes 14-18. The Royal Wulff, a hair-winged variation of the time-honored Royal Coachman pattern, floats better than the original and is much more durable and visible. Originally intended for larger hooks, the pattern seems to be more effective in smaller sizes.
Ausable Wulff, sizes 10-14. Tied with a reddish-tan body and a mixed brown and grizzly hackle, this pattern performs a passable imitation of Eastern March Brown and Gray Fox mayflies. Its hair wings and tail make it much easier to fish in rough water than the original ties for those species.
Parachute Adams, sizes 12-20. Hands down, the title of "best generic fly" goes to the Parachute Adams. Its gray and brown coloration might not catch anglers' eyes, but it sure catches trout. The original Adams was nearly invisible on broken water. The parachute version's white calf-hair wing is much easier to spot.
Light Cahill, sizes 12-18. Late-spring mayflies tend to be small and light-colored. In a pinch, a Cahill can fill in for a Gray Fox, a Pale Evening Dun, a Pale Morning Dun, or any of several Sulfur species.
Little Blue Quill, sizes 16-18. Small, dark mayflies are tough to see and tough to fish. When they hatch, it pays to have a few Little Blue Quills on hand. They're often the ticket when trout appear to be rising to Green Drakes or Sulfurs but won't take the light-colored flies.
Griffith's Gnat, sizes 16-22. Midges come in zillions of shapes and sizes, and there's no way to imitate them all. With its peacock body and palmered grizzly hackle, the Griffith's Gnat creates a could-be-anything silhouette and makes a fine generic midge pattern.
Deer-Hair Ant, sizes 12-16. Even finicky trout can't resist ants. I prefer deer-hair patterns because they float better than those tied with fur. A tiny tuft of bright yarn, tied to the ant's back, helps make it more visible and makes strikes easier to identify.
Letort Hopper, sizes 8-10. Letort Hoppers aren't the most fancy patterns, but they're easy to tie and don't take up much space. Their deer-hair heads make them buoyant, and their relatively streamlined shape makes them easy to cast.