One of the best things about having a 3d Printer

Yep. My most successful spare part to date was a little clip that holds the cover on my old Lian-Li computer case. There was one for each corner, and one of them broke, so I scanned the pieces in, joined them back together with gimp, converted them to an svg image in inkscape, and used the inkscape plugin to generate an openscad version of the part when allowed me to generate an .stl I could print. Used almost every tool on my computer :-). Best of all, the replacement clip actually worked, no floppy corner on my old computer anymore.

http://home.comcast.net/~tomhorsley/har … epart.html

Excellent! That's all I have to say.

One of the best things about having one is for making gifts for friends and family.  Let's say your friend wants a energy sword replica for his birthday, just fire up the printer and BOOM. I have also made tools and parts for myself, very handy.

The ones in my picture above I think are the most useful.

A lot of people experience failure of their bearing mounts. I want to be prepared if mine ever do.

I think it's only a matter of time because the factory ones are pretty weak.

I will be installing stepper motor vibration pads soon and may swap out my mounts anyway as a pre-emptive measure.

Edit: Forgot to mention the bed-leveler adjusters are nice to have as well. They are certainly better than the thumb wheels that ship with the printer.