What is a synonym for Gadzooks?

There isn't a single perfect synonym for "Gadzooks" as it's a rather archaic and whimsical exclamation. However, depending on the context and the tone you're aiming for, you could consider these options:

For surprise or astonishment:

* Goodness gracious!

* By Jove!

* Good heavens!

* Well I never!

* Crikey!

For annoyance or exasperation:

* Blast it!

* Confound it!

* Drat!

* Oh, bother!

* Shoot!

For amusement or lightheartedness:

* Gosh!

* Wow!

* Dear me!

* Fiddlesticks!

* Well, I'll be a monkey's uncle!

Ultimately, the best synonym for "Gadzooks" will depend on the specific situation and the desired effect.