This tee is supposed to be from 1994. It's all black, with a big full color, shaded design on the front. It has classic getting ready to run Sonic, but they have added various pieces of purple rock / rubble /cement flying off from around him. This makes the design suggest he's 'bustin thru' something like a wall or barrier. The logo has been altered a bit, the "Sonic" part is written vertically and appears somewhat squeezed, while "The Hedgehog" is much smaller, horizontal, and at the bottom. You can see the copyright there under the smaller 2 rocks. This is probably a smaller teens size tee.

Photo discovered by The Tumblex

Now here's something that's seriously uncommon...
Sonic Scrubs! Specifically, the shirt part to a 'scrubs outfit' which is what doctors, nurses and sometimes other medical type professionals wear as a clean-able uniform. They're not sold to the public, so that adds a layer of rarity as well. For use in areas where kids are patients, the scrubs are sometimes decorated with cartoon characters to put them more at ease. In this case, a company got a Sonic license...and used it to create altered stock art that's probably only found on this specific item. (And pants, if it also had pants) It features standing Sonic, but holding a giant tooth brush, Sonic showing an X Ray photo to Tails, & what appears to be Sonic & Tails talking about something, but with the folds it's impossible to see what. There are also little tooth brushes and stethescopes scattered around as part of the pattern. With the altered stock art, & general uncommon-ness, this is an interesting item to see! 

 Photo by @JapanAnimePosters on Instagram

Here's a cool old jean jacket.
It's the usual blue jean color, but with a really large/nice Sonic embroidery on the back. It's the lesser-used stock art of him in the directors' chair, and they've added a megahpone to his hand. Sometimes this art has him wearing sunglasses, sometimes not. This one has it, and also gives him a rather large mouth. Notice the megahpone-holding hand though, it only has 3 visible fingers and they're not too great looking. Whoever modified the art didn't get it perfect. There's a small "Sega" logo on the front chest area & the back/interior has a leather tag. But, what is Sega Studios? Why did it have jackets made & how could they be obtained? It's likely an 'industry' item, which makes sense that it wouldn't be common since it wasn't for the public. 

A little bit of an unusual old tee featuring AOSTH Robotnick. Show characters were seldom featured on USA merchandise, even back when the shows were airing. (X was the first to get tons of stuff) This black shirt has rolling Sonic, the logo and slogan "Sonic Spin". But it also has running Robotnick as 3 overlapped graphics, probably for the 'movement' look. However, it makes him sort of confusing to look at due to where he's placed, and the size. The 'echoes' aren't like the usual after-images Sonic gets, because the furthest back one is somehow also the largest, and they're all in color/just as bright and not faded. It's an interesting enough sort of campy classic design though.

This is a rare, promotional tee.
It is adult size men's white tee released only in limited quantities to promote Sonic Spinball on the Genesis. The front has the less-common air-brush somewhat-abstract pinball art (notice Eggman at the top) & the back has the game's logo across it. Front & back printing isn't that common. The slogan "Spin Into Action" is written above the graphic. This MAY be a Babbages pre-order item.

 Photo by @JapanAnimePosters on Instagram

Here's a rare jacket that's got to be an 'industry item' that wasn't for the public.
It's either black leather or faux leather & features a large Sonic patch with fabric & embroidery. It's finger-waving Sonic in a yellow ring, but instead of white wings beside the ring, it has sort of pointy red shapes that go into a triangle at the bottom. The title ribbon is blue & squared off. Notice the patch below it. It reads "Sega Technical Institute Redwoody City, CA USA Sonic Team"
So, this had to be for game developers or someone who worked during the Redwood City location era. There were probably only enough of these specific patch/jackets created for the number of project members on...whatever this was created for. Very interesting to see, and certainly uncommon!