The question should actually be more location specific...........WCVI in August = big spoons, big plugs, & purple and black label herring.....Also some spots in puget sound during summer where needlefish are prevalent and small spoons and needlefish hootchies kick a**
Thru the years I've learned that the most consistently successful fishermen have more than a handfull of "go to" lures to match the available food source where and when you are fishing. From Pilchards to needlefish & plankton and everything in between. "Match the hatch to increase your catch".....BTW, if we all only used one lure, then we would all have enough savings to retire and most tackle shops would be out of business, and the wife would actually encourage us to go fishing.
If I did have to choose just one it would be the 142R green speckleback hootchie w/green glo flasher.