T-shirts are the most universal part of anyone's wardrobe. I've found several stores that sell really unique tees, but my favourite has to be Super Superficial. The artists they feature are mostly independent artists, with a freedom to create anything they want on a t-shirt. The ones I've bought in the past are; Grizzly by Tom Baxter, Boat by Mike Perry, and Disguise by Nina Bunjevac.
Excuse the quality of them (I can't wash my clothes properly!)
Boat by Mike Perry
Disguise by Nina Bunjevac
What is also awesome about Super Superficial (aside from its name), is the stamp system they have in place. Every time you purchase a shirt, they give you a stamp (they also give you a free stamp from signing up!). If you get 10 stamps you get a free shirt.
These are some of the shirts I'm currently drooling over.
Deer Oh Deer by Tom Baxter
I are Walrus by Patrick Seymour
Crash by Jasper Rietman
Parrot by LNY
There's just something about the artists Super Superficial work with. Their work is very witty, and fuckin' creative! If you are planning on getting a shirt, make sure you don't mix your whites and your colours!