For me:

• Thinner boning/fish knife for finding cartilage seams between bones, or deboning certain cuts. My chef's knife is too big to navigate a curved path through meat, at least not precisely.
• Thicker/heavier cleaver for cutting through bones directly. I don't want to chip my chef's knife blade on very forceful cuts.
• Rectangular Nakiri is great for chopping firm vegetables with a blade edge that's in a straight line, rather than the curved edge of a chef's knife (which usually calls for a rocking or slicing motion when chopping).
• Serrated bread knife for bread. I don't want to be crushing a freshly baked loaf too much while slicing into it.
• Cheap/shitty serrated bread knife for ice.
• Long carving knife for presentation, tableside carving of a roast or ham or things like that. If I'm carving back in the kitchen I'm probably just using a chef's knife rather than grabbing something new to have to clean.

Everything else in the kitchen, I use a chef's knife. I had a one-knife kitchen for like the first 10 years of my adult life, before branching out to a vegetable knife and a boning knife. The other stuff is more recent (ice knife when I got really into cocktails around 2015, bread knife when I was part of that sourdough craze of 2020).

I also have knives for serving (butter knives, steak knives, cheese knives for charcuterie platters, etc.), but that's not really a kitchen function.