This isn't financial advice, but if they dropped 40-50%, things like consumer staples would go up. In fact, they did this Friday, when everything else melted.

The best defensive stock for those situations is WMT, but you can think of other similar names as you reason through the why. That's where I'd go. There are many ETFs such as VDC (Vanguard Consumer Staples).

If you don't want to be so defensive, you could go VTV which is basically "large cap value stocks" so it still includes some Tech like Intel but it's way more diversified into other industries.

Gold is more inflation-related, so I wouldn't go there, at least not for the 40-50% draw down scenario you're describing.

Small cap value did well in the 2000 tech crash and SP600 (small cap) doesn’t have many direct datacenter or AI exposed names compared to large and mid cap indexes. But given the scale of capex across the US they aren’t immune from secondary effects.

Probably an international fund like VEA that is much more diversified.

I think there are no safe harbor investments at this time. Even gold is unpredictable.

Personally I went 80% world excl US and 20% equal weight S&P500 to hedge against what I think is an AI bubble. But if the market decides to adjust Nvidia's valuation 20% downward next week, I expect there to be ripple effects throughout the economy.

(Like the .com bubble, I think the tech is genuinely transformative and here to stay, but the valuations are just ridiculous.)