Oh dear! Reading this thread made me realize that I am VERY brand loyal and picky. It's easier for me to list what I will "go generic" for than the other way round.
I never buy books or magazines for myself. I borrow them from the library. (I read the mags one month old when they turn into lending status).
I rarely rent grown-up DVDs. I *do* rent children's DVD because in our town, they are cheap ($1.99 with no late fees) and the children's DVDs at the library are always in horrible condition. We do often see movies in the theatre - that's usually a "date night" for DH and me.
Paper towels. Any kind, store brand, no-name generic is fine. The only thing I am picky about is that I always choose the "select-a-size" type.
Paper lawn waste bags. Don't care about brand, just a cheap price.
We don't have cable. (And in Canada, that's saying something!). We wait the 48 hours and download our shows from the internet.
I don't have a fancy cell-phone service. $100 prepaid for the year, and we're more than willing to switch providers at the end of any year.
I agree with many of the PPs. When we were younger, and just starting out, DH and I pinched our nickels until the beaver squealed! Cheap no-name (generic) EVERYTHING. The day we could afford brand-name toilet paper was a happy, happy day!

But we have since found that in many things, you really do get what you pay for. For us quality is important because we are really trying to reduce our consumption. So I'd rather pay twice as much for something that last four times as long, than go cheap and make more garbage to send to a landfill.