more cowbell
n. Something extra that will take a project or endeavor to a higher level.
Examples
2006
I expected half of Austria to storm the Italian border, clang their cowbells like madmeisters and blow their fluegelhorns at the men's downhill, their Super Bowl. Wrong. We needed much more cowbell.
—Chris Jenkins, “Passion appears to be on holiday at events,” The San Diego Union-Tribune, February 16, 2006
2006
The show had a little bit of everything, from dancers, flaming inline skaters, blacksmiths and fake cows rolling around to a K-tel soundtrack for the athletes' parade. Could have used more cowbell, though.
—Steve Schrader, “Maier 'fans' are drug testers,” Detroit Free Press, February 11, 2006
2002 (earliest)
Robert Morast needs more cowbell.
—Robert Morast, “Spice up school curriculum with your own flavor,” Argus Leader, August 30, 2002
Notes
Don't fear the cowbell. Once a herding tool for wandering beasts and later a percussion pariah, the humble rhythm tool is now hip. With the release of Maximum Cowbell, a 16-track collection of classic rock songs that employ its trademark hollow clank, the cultish fascination that began with a Saturday Night Live skit in 2000 grows.

The comedy bit involves a fanciful account of the seventies recording session that produced Blue Oyster Cult's soft-rock hit Don't Fear the Reaper. Christopher Walken portrays Bruce Dickinson, a producer intense in his belief that the track requires something extra — specifically, "more cowbell."

Up to the challenge is Will Ferrell, the writer of the skit and a master at bumbling, occasionally destructive physical comedy. With the barnyard gong in hand, Ferrell bangs away at the cowbell urgently, although in perfect time.

The rest of the band is dubious, but Walken's character is insistent. "I gotta have more cowbell, baby!"

The repercussions of the sketch continue. Now part of the pop-culture lexicon, the catchphrase "more cowbell" refers to anything that needs a little something extra.
—Brad Wheeler, “You gotta have more cowbell, baby,” The Globe and Mail, April 06, 2006