Or, how about this? It's the perfect "throwing something on when your back from the dead brother surprises you with a visit" shirt.
There's no better shirt to fall back to when getting punched by your livid brother after he finds out you've been sending demons back to Hell with your mind. It's durable enough to be grabbed by said brother while he's pushing you toward a wall. It also provides comfort for the extreme guilt trip after having the fear of God drilled into you.
Remember Sam when you were under a siren's spell and told your brother he was worthless and weak? Yes, go to your favorite piece in your wardrobe when trying to smooth over things with Dean. Judging by the guilty look, he may have put too much faith in the shirt.
How about this heartwarming scene? The red in the rolled up sleeves matches the blood from the bandages.
Or the perfect shirt for comforting his recently kidnapped and distraught over giving up his perfect life brother?
Yes, the white shirt. It's a tragedy against fashion, yet it's so him. It's old, ropey, and Sam has been through some pretty weird situations in it. So far, I've determined it's first sighting is "Children Shouldn't Play With Dead Things." Remember, Sam broke his hand in this shirt.
How about this fond memory? Sam finds out his father's parting words to his brother. Dean has to save him or he'll have to kill him. At least he had he found out such a horror in comfort.
So, it's time for the fan participation of this homage. Name Sam's shirt! You can call it Norman or Sheila, or come up with something like Sammy's shirt of doom, I don't care. The top suggestions will be put to a poll vote. Or, in the case of the countdown clock contest, the one person who submits something will win! The winner gets a mention on a tweet and I shall from this point forward call the shirt that name in future recaps. Heck, "What Is and What Should Never Be" is next on my classic episode recapping list, so I'll do it there too during the next hiatus.
For those that are really creative (fanfic writers, I'm calling you!) write the story of how Sam found that shirt. Just post it in the comments. Winner again gets prestige and mention in a tweet. I know there are bunch of a creatives out there. Let you freak flag fly! After all, after four seasons, Sam's shirt has earned an identity. Let's give it one!