This is called the "Sketch Hero Tee". It's meant to look like a page doodled into a notebook. You can see the blue lined paper 'background' & Sonic is scribbly colored in, as if with a pen or colored pencils. So are the lightening bolts at the top & doodles around the logo. You can also spot Eggman down in one corner, Metal Sonic above him, Knuckles near a 'sound effect explosion' & Tails jumping over the word "Bloop" at the bottom. There are also little rings and stars scattered about. Everyone but Sonic is mostly a line drawing. This shirt design is very unique, there's no other tee out there like it with this 'sketchy page' idea. This is a 2014 item.
This is an adults sizes white tee. It has modern Sonic & Tails in full color. The lettering is sort of blocky font 'varsity style' text, which has a weathering effect applied. Curiously, the design itself does not, which is nice to see. This was described as a "Ladies Tee", but really, there doesn't seem to be anything particularly ladies about it, so probably anyone can wear it. This is a 2014 item.
This shirt is titled "Run the Street", & the design is all CG. It's actually Sonic running down a hill from the City Escape level (where you were chased by the GUN truck) or the similar level from Generations. Either way, the street & buildings/background has been lightened/faded. This is an adults size white tee. This was discovered in 2014, but where is it sold?
Just as with that 'rainbow outline' black Sonic tee, this shirt was released twice, the second time, the design used glowing ink for an extra cool effect. This one features modern 'pointing outward' Sonic, but half of him is transformed into a surface grid overlay of green lines. Technical background features like a gear, arrows & circles are added. The slogan is "Built for Speed". That round green sticker up at the top there says "Glows in the Dark!" Anywhere there is that hot green ink, the shirt will glow. This is at Sears in fall 2014, & should be in the boys/teens area for about 8 dollars
This could be the third "This is what Awesome looks like!" tee. The first had classic Sonic, the 2nd had modern with lowered-peace-sign hand, and this one has turning thumbs-up. Sonic is shown in a ring of white stars, with the modern logo small above his hand. Because the shirt is red & the design is printed on, do watch out for fade through if it gets used a lot. The slogan is quite true though!
This turquoise tee has an off-square grid featuring 9 characters. The cool thing is that they chose Eggman AND Metal Sonic for 2 of the squares, so it's not just good guys & provides some variety. You can see Sonic, Tails, Knuckles, Silver, Shadow, Metal, Eggman, Big & Vector. (Vector's a bit random though, where's the rest of the Chaotix? Why not pick Blaze or Rouge instead of isolating Vector?) The bright colors, fun shapes & great variety of characters makes this a nice tee.
This shirt is from Epic Threads in 2014. It may be using Riders art, or at least Sonic with some green goggles as the main art for the design. It's a slogan tee, and says "You Dont have this Speed Bro!" That white vertical thing to the right of the design portion is a sticker stripe of "Medium"/not part of the tee. The modern logo is at the bottom. The words are stylish, half cut out of the background as negative space. This tee comes in adult sizes so anyone can wear it. With Sonic being mostly-backwards, it's also pretty fresh looking.