My day-to-day wardrobe almost always consists of t-shirt, jeans/cargo pants (or shorts, depending on season), and some sort of additional shirt. For some reason, I get real self-conscious when I walk around in just a t-shirt, and need an additional layer just to feel comfortable (even in the hottest days of Summer, when most people would want less layers, I need at least 2 shirts on).
In the Summer, I'll wear one of three different short-sleeved Dickies® work-shirts over whatever t-shirt I'm wearing that day. I usually wear it unbuttoned, so as to show off whatever clever picture or slogan happens to be on that day's t-shirt.
Alternately, I'll sometimes wear a thin, longsleeved shirt with the sleeves rolled up. A couple of them are actually designed to have the sleeves rolled up, as each sleeve has a button just above to elbow to keep it in place when rolled.
In the Fall/Winter/Spring, I'll wear zippered hoodies (which I prefer over non-zippered hoodies). In the past, I usually wore black or dark gray, but over the past year I've been wearing a lighter gray with red sleeves and hood.
Like this, only not from Old Navy
I also have a soft spot for flannel shirts, but currently only have a lone red-plaid flannel that I wear a lot (weather permitting).
When it gets really chilly out, I tend to wear my hoodie along with a leather vest that I had bought a couple years ago as part of a Halloween costume, but liked the look of it. I wear it every chance I get.
I have numerous jackets and coats, as it seems every Winter at least one of my family members thinks I need a new coat or jacket. The oldest one I have (which I should probably retire soon) is a sturdy old Carhartt which I've adorned with various patches over the years, including a couple NERV patches from NGE, a Capsule Corp. patch from DBZ, and a couple band patches such as the Nine Inch Nails logo.