Trinkets
Any clothing from the Schlock, Something Positive, Ninja Burger, or anything you thought looked cool, sections of Warehouse 23 (www.warehouse23.com)

Basically, nerdy t-shirts and hats are nigh-impossible to go wrong with.

That said, Threadless.com has some hilariously eccentric t-shirts.

Also, http://www.thinkgeek.com/apparel/hoodies/8064/ that hoodie looks pretty sweet.

Also, http://www.cafepress.com/usingrights.12230720 looks pretty random.

Of course, there's also http://www.zestuff.com/product.php?productid=185&cat=6&page=1
or really anything from there.

Books (TPB - trade paperback, those relatively thick bound-together versions you find in the Comics section of B&N or such)
Invincible TPB 6+
Sin City TPB 3+
Lucifer (by Mike Carey!) TPB 2+
Any of the Hellblazer TPBs except "Original Sins"
That said, just feel free to either ask some nerdy looking clerk or randomly pick trade paperbacks off the shelves. As long as it's not anything from Sandman (have it all), Fables (again...), Watchmen (again...), or the Runaways hardcover (again...), or something from outside of the numbers listed above this paragraph (IE: I have Sin City 1 and 2. I have the Invincible TPBs before 5.), you'll be sending me a pleasant surprise that I don't own.

Again, feel free to just ask some guy in the store for recommendations on science fiction, and mention that I like Terry Pratchett and Neil Gaiman, and have already tried Neal Stephenson. They'll find something.

Games
Guild Wars (PC)
Half-Life 2 (PC)
Age of Empires III (PC)
Megaman X Collection (GCN)
Animal Crossing (GCN)
Master of Orion 3 (PC)
Pokemon FireRed (GBA)
Pokemon LeafGreen (GBA)
Pokemon Ruby (GBA)
Pokemon Sapphire (GBA)
Pokemon Emerald (GBA)
Megaman Battle Network 5 (either) (GBA)
Megaman Battle Network 6 (either) (GBA)
Megaman Anniversary Collection (GBA)
Baten Kaitos (GCN)

Computar Stuf
Intel PWLA8390MT (http://www.newegg.com/Product/Product.asp?Item=N82E16833106105)
Any (http://www.newegg.com/Product/Product.asp?Item=N82E16822152011) of (http://www.newegg.com/Product/Product.asp?Item=N82E16822148093) these (http://www.newegg.com/Product/Product.asp?Item=N82E16822148032) hard (http://www.newegg.com/Product/Product.asp?Item=N82E16822144174) drives.
Blank DVD+R or DVD-R media is always cool. Stacks of 100 from newegg.com or some huge deal site are usually your best bet. Anything over 30 cents per disc is not worth it.

Other things
If you want to give me something and don't want to just randomly buy something off the
above list, please just get me a gift card to a bookstore - or money directly. Computer
store gift cards are worthless, as I do almost all of my nerdy buyings on Newegg.com,
and obviously CompUSA gift cards aren't useful there.