I pretty much liked the majority of HB sound effects, since they were used in a lot of series. Of particular note would be the sound effect that's first heard when Jet Screamer makes his spin entry on The Jetsons. This would be later used whenever Winsome Witch used her magic (remember her catch phrase Ippity-Pippity-POW!!!), among other series. That last time it was used was for one of HB's final logos, the rectangle that had stars from several series including Flintstones, Jetsons, Yogi Bear, Huck Hound, El Kabong, and Scooby-Doo dashing all over the screen. The sound effect added a couple of bings, bangs, and boinks at about the point it would freeze on Fred Flintstone.
My least favorite sound effect was in the original Spider-Man series in the late 1960's when that annoying zip noise was made whenever he swung across the screen. It was omitted in season 1, but for the last 3, it was an unnecessary addition, after the second animation studio practically took away other good aspects of the superior first season.