The Clouser Minnow is arguably the most versatile fly in the world. A baitfish imitator, it can be tied in any size and color to match the local forage.
Note that the fly is actually tied "upside down", with lead or bead-chain eyes on what would normally be the top of the hook. This inverted tie allows the hook to ride point up, as the eyes impart weight and the wings act as a stabilizer - the fly is almost weedless and almost always results in "top lip" hook-ups.
I normally tie it on a #4-2/0 hook with a white bucktail body/wing, a bit of flash, and maybe a colored overwing. I like the Clouser tied very sparsely - remember most baitfish are at least partly translucent. Most tying instructions say to tie on a clump of bucktail to the
hook shank while it's right-side-up, before tying on the eyes. Per a suggestion from Lefty Kreh, I omit this step.
The Clouser shown above is tied in "Bead-Rattle" style with
sliding bead on hook shank and wire "bead stop" at rear of hook
shank. See the FLY TYER Magazine
article for details and tying instructions.
The Clouser, in varying sizes, has worked for me on black, white & hybrid bass, bream, trout, redfish (red drum), spotted
seatrout, mangrove snapper, jack crevalle, barracuda and snook.