I feel like a hoarder. I have three PPC Macs that used to be primary machines for either my wife or me. Right now they are mostly used as a hobby for me and we don't really have a place to keep them out and such. My wife has a late 2008 MacBook (though she does most of her stuff on an iPad these days) and I have a 2012 Mini with maxed out RAM (16 GB which really helps when running Windows 7 in a VM under Fusion), both running Yosemite, but sometimes I want the feel and nostalgia of these older ones, and to use some of the old apps and games they ran on.
First is a Pismo PowerBook, upgraded to a G4/550 card, 1 GB RAM and a 60 GB hard drive, running both OS 9.2.2 and 10.4.11. It has an aftermarket PC card for wifi which "overrides" the early generation AirPort card so I can connect to my WPA2 network.
Second is a "Digital Audio" G4, originally 667 MHz with a Sonnet upgrade card to 1.47 GHz. It is maxed with 1.5 GB of RAM and has an 80 GB hard drive, and runs both 9.2.2 and 10.4.11, and I use a wireless Ethernet bridge for connectivity to my WPA2 wireless network. I have toyed around with the idea of an SSD and a dual boot with Leopard on this one (which can be done with unsupported tweaks), but haven't yet. It's mostly a hobby and I can't really justify the cost of an SSD, even a small one which costs under $100 these days. This is the Mac I'm posting this comment with.
Finally is a 1.33 GHz, 12" aluminum PowerBook, all stock except for an upgrade to 1.25 GB of RAM (again the max for that system), running 10.5.8. (Can you tell I like to max out my RAM?)
In terms of engineering and design, the Pismo may be my favorite Mac ever, and it's still marginally useful for some tasks today.