I think my Mac mini will always be my favourite Mac of all time. Sure, I haven't had a lot of the older Macs, but there's something about the mini's form factor that I just love.
My very first one was DOA, so all I could do was hold it and look at it. And hold it and look at it I did - I could barely put the thing down! 😉 Such a great, compact package. Having a working one is even better of course, there's a lot of punch in my 1.66GHz CD Mac mini (the original Intel one) with its two gigs of RAM.
Yes, I've had to replace the HDD (and wow am I glad I did, the 500GB WD Scorpio Blue is just a terrific drive), but otherwise it just gets on with things. It runs 24x7 and houses my entire iTunes/AppleTV library. It's quiet, pretty cool, but most importantly when I do want to use it for something it doesn't lag at all - it feels as quick as any other Mac I own for basic tasks.
Only thing that lets it down is the wireless. It's pathetic. I have to use a wireless bridge, connected via ethernet, to keep a stable connection to the AEBS, and it was the same story with numerous Linksys and Netgear routers, too.
I just love it. I hope it lasts forever.