First of all, I dispute that this is actually a "t-shirt". Regardless, I love the Del Mar...top from Aritzia*.
It's cozy and you can size up for a casual look or size down and dress it up with a cute necklace. You are probably appalled at the amount of grey in my collection, but a couple of them have been purchased in a larger size to wear to and from the gym. I can throw one on and run a quick errand without looking like an Olympic athlete (okay, there are many other reasons why I'll never look like an Olympian but we'll save those for another post...)
If you're not into a longer look, try the Pomona -- the v-neck kinda sexifies things.
Let me know what you think!
*yes, I'm on a bit of an Aritzia kick right now.