Hope it's ok to make a list: My thought was,"if 1 is good, 2 must be better"! Sometimes 4 or more.

Very expensive (thousands of dollars for a) sewing/embroidery machine with expensive software. More than I'll ever learn to use.
Another embroidery program. What was I thinking?
Fabric
Pounce x2
PVC hand quilting frame. Would love to sell it.
FabuMotion Fabric Mover. Would love to sell it.
All kinds of rulers. Found I use the same ones over and over!
Tons of markers
Storage containers of all kinds.
Clover needle threader that I can't figure out how to use.
Lots of thimbles. Use one cheap old thimble of my mothers. I taught myself how to use it.
Way to much thread, cotton, polyesters,embroidery threads,in just about every color. A plastic bed bag full of serger thread.
2 sergers which just sit on the shelf
Too many sewing machines
Several tables that didn't work in my room. Gave 3 away.
Equilt 7
Scissors out the ying-yang
Drawer full of bobbing thread with 4 plastic bobbin holders that I haven't used.
3 extra cutting mats that I don't use
A wall full of all kinds/sizes of rulers and mostly never used
Cameo Silhouette and all the notions to go with it. Used it once.
Several sewing rolling bags plus: Do have one for the large sewing/embrod./arm. One for the FW. And one for the Serger.
This list is too long to add anything else. LOL!

Only if I had just started using the old Kenmore I had and bought enough fabric and one ruler to make a quilt. Hindsight is like Monday morning quarter-backing. I can't believe what I have accumulated in 4years!!! At this point, I am buying little to nothing. I could have saved thousands and thousands of dollars and still had fun quilting for it is just a basic sewing hobby: a sandwich of 3 pieces of fabric, cut apart, and sewn together... I think my learning curve was just a bit big and slow.... But I love it all and will keep on quilting!!! And embroidery here and there!!

a serger machine--brought it home, opened it up and read a lil, put back in case, put machine away with extra sewing machines for 'A Some Day' experience--maybe in 2015 !

I bought the Steady Betty pressing board and the small cutting mat that rotates. Although both are very nice tools, I seldom use either.

This is a great thread. I'm in Australia so some of these things I haven't heard of. I do have the GO Baby and have used it several times. I like it for the time saving and accuracy of the shapes cut. I think Magazines and books are my weakness. I was watching a youtube quilting show yesterday and loved the wedding ring quilt they were making so have ordered the book with the special template off Amazon. At least I can rewatch the show to figure it out. I do have the EQ7 haven't used it much haven't even watched the tutorials through. Must find Rhonda tutorial.

I originally bought the pounce pad for hand quilting, but did not use. When I got my longarm it decided pounce pad would be great for marking as I go! Well, you can pounce on the design, but soon as I turn on my machine to quilt,the speed of machine makes the chalk bounce all over and you can't see design. I did end up pouncing design then marking over with wash put pen! double work. At the next big show I ask the salespeople about this "vibrating chalk off fabric" situation. She said "after rubbing stencil several times with pounce pad,spray with hairspray!" I have never tried this because all I can think of will happen is my longarm will gunk up with hairspray! So No to pounce pad!
I really like my accuquilt. I am English paper piecing 5/8" hexagons and loved my accuquilt to cut hundreds of 2"squares. great for strips too. I've found dies on eBay cheaper but agree they are way to pricey.
I also love the binding clips. the clover bobbin holder was waste of money! the don't stack well and fall over.
big fan of books and magazines, but I am trying to cut down, so my sewing area doesn't look like episode of hoarders! I find flipping the pages while drinking my tea very relaxing and cheaper than therapy.
have never used the "curve master" foot attachment. Also have the Alto Cut (original one) I bought on eBay, which has never been used.
Have enjoyed this thread many items I have thought about discussed. And as you can read, I'm a big sucker for a flashy demonstration at a quilt show!

The rotary blade sharpener......

My go to ruler is Quilt In A Day's triangle square up ruler. One cut and done.
The Flynn frame was my worst waste of money and gave it away.

I agree....pretty useless

I bought a very long ruler that has the grit on one side that's supposed to sharpen your blade as you cut. Nope! It dulls and scrapes up the blade while making a gooseflesh-raising sound instead. Fortunately the grit is only on one side so I can still use the other; it's yardstick length & useful for trimming finished quilts, but I'm sure I paid extra for that horrible grit.

I also wish I hadn't wasted money on a spinning mat, now I just use a small mat on top of my big mat, but that "small" mat is larger than my spinning mat, so the spinning mat just lives in the closet, virtually unused.

I wish I hadn't bought most of my Omnigrid/Omnigrip rulers and had spend the money on Creative Grids or Olfa or other more clear-to-read rulers instead. All those thick yellow/green lines are really hard for me to see through.

I think that's about all that I really regret. I suppose that's a good thing, as I've spent a LOT over the years!

Hmmm....as much as I love my top-of-the-line sewing machine (Pfaff Performance 5.0), I've found that I really don't NEED all those fancy stitches and optional presser feet I just had to have when 90% of what I do is strait stitch piecing with my 1/4" foot!