My needle threader is 6 foot tall and weighs 200#s......;)
I have vision issues, and I totally depend on my sweet hubby to thread my needles.

I use the desk clover threader too. The only trick is to make sure the thread tail isn't too long before pressing the leaver. I use a dental floss loop to thread the embroidery thread. They come in a little plastic container. Someone here suggested it and it works for me as long as the eye of the needle is large enough to accommodate the straight plastic end to go through. The self threading hurts my fingers after a short while, so only short jobs for these, at least for me.
I also bought a lighted magnifier that fits around my neck when the light is low. Like in front of the T.V. at night.

I use the Clover needle threader. I use it a lot when I'm doing EPP. I've had good luck with it. No, it doesn't work every time. I do have threading fails, but it works well if I use to correctly.

Can't remember the brand, but bought my sis a combo magnifying, lite, glass that has a holder for the needle and while it has a handle so you can hold it, it also sits firmly on a table. Cost about $15--she has a cataract that is still "not serious enough" to have removed and does handwork all the time. She loved it!

I use the Clover desk threader, like many others here. If it doesn't work for you, it's possible the hole of the needle is facing the wrong way. You do have to be able to see well enough to place the needle in the holder so the eye of the needle is facing the thread. If you have the needle rotated so the eye is facing you, it won't work.

I was at a quilt show yesterday and one vender had a double needle threader -- one side threaded small-eyed needles and the other side threaded the "Big Eye" needles. I did purchase a miniature needle threader at Hobby Lobby for $1.99. WalMart sells a needle threader with a light on their notions wall.

For the larger needles, the dental floss threaders work very well. Google dental floss threader for a picture of what they look like. In the toothpaste aisle. There are many different brands.

I have had two Clover needle threaders....neither one worked on anything but Clover needles. I complained to the retailer. No response. I tried various other needle brands and sizes. I do not want to use clover needles....so these have gone in the trash.

I have the clover threader and it works for me. sometimes I have to take the needle out and turn it and put it back in, or push the lever slowly or push the lever quickly...it works the first time 90 % of the time.

I have both the Clover and the Bohnin (sp) threaders. They both work well, but you have to make sure to read the directions and have the thread all the way down, and not held too tight so it can be pushed thru by the wire in the little machine. I also have a small wood piece that the Clover sits in and it works better. I bought it at the SD Quilt Show many years ago and someone at the booth made them. Has a grove on the wood and a piece of 2 sided tape holds it in place.