When I'm at work I have a mini multitool in a cargo pocket for fixing random stuff around work, a big locking folder that just gets used for big tasks or when I need a long blade for eating with, and a cheap, medium sized traditional 2-3 blade folder in a shirt pocket for regular stuff and the rare occasion someone wants to borrow a knife and I actually let them. It gets abused a little because of the low price, but I like the way a traditional feels so its what I use. Also at work I carry a Mora Electrician for use as a box cutter, but its just used for opening and breaking down boxes since its faster than opening a folding knife.
At home or out and about, I swap the Mora and mini multitool for a "belt knife;" like a big multitool or occasionally a fixed blade. Sometimes I carry a large folder in a belt pouch instead though. I carry multiple knives because they're for different uses, but also because its just fun to. I think a big part of it is "why the heck not?"
There's also a Gerber Shard on my keychain, that thing gets used a lot. Definitely one thing Gerber did a good job on making.