I choose GBP/USD.
GBP/JPY usually has great market structure.
I would go with XAU/USD.
CAD/JPY is my choice; for some reason, I can predict it quite easily.
USD/CHF is my pair.
It really depends on the market conditions and trading setups; sometimes you need to adapt.
I used to trade everything but now stick to three: USD/JPY, BTC, and XAU. If this fails, I’ll just focus on USD/JPY.