I'm going to put forth my suggestion, which is a little different than most you'll see on OCN. It goes for an Intel build to get a more powerful processor than the AMDs on offer, but since I'm infering that your friend doesn't want to bother much with the hardware side, I'm neglecting overclockability to save costs. This is kind of assuming that he (or you) don't want to bother with setting up an overclock (I'll also point out how to change the build to allow for OC).
Replacement parts for overclocking build:
Warning: Spoiler! (Click to show)
CPU - i5-2500k $200
http://us.ncix.com/products/?sku=57962&vpn=BX80623I52500K&manufacture=Intel&promoid=1058
$34 less than the slightly improved update, i5-3570k. More expensive than AMD processors, obviously. Normally you'd get a non-K processor if not overclocking, but the i5-2500k is on sale for less than an i5-2500.
Mobo - Gigabyte cheapo H61 $55
http://us.ncix.com/products/?sku=63501&vpn=GA%2DH61M%2DS2H&manufacture=Gigabyte&promoid=1058
It's a no-frills mobo, but hey, they work and save you money.
GPU - Radeon 6870 $160 AMIR
http://www.newegg.com/Product/Product.aspx?Item=N82E16814150521
The 6870 is only a little worse than a 560Ti, but $50 cheaper. This particular one has a higher upfront cost, but a $30 rebate. It'll run BF3 fine unless your friend is one of those guys that loves to crank the settings way up. Then you'll have some problems staying in budget in any case.
RAM - 2x4gb 1333mhz RAM - $30 w/promo code
http://www.newegg.com/Product/Product.aspx?Item=N82E16820313086
Case: haf 912 $50
http://us.ncix.com/products/?sku=55583&vpn=RC%2D912%2DKKN1&manufacture=COOLERMASTER&promoid=1058
One of the best budget cases.
PSU - Antec Neo Eco 450C $30
http://us.ncix.com/products/?sku=60491&vpn=NEO%2DECO450C&manufacture=Antec&promoid=1058
Quality, clean power on special.
DVD-burner $17
http://us.ncix.com/products/?sku=49597&vpn=DRW-24B1ST%20Bulk&manufacture=ASUS&promoid=1058
SSD: Crucial M4 128GB $125
http://www.newegg.com/Product/Product.aspx?Item=N82E16820148442
Load OS & most commonly used programs on it. Your friend will love you forever.
HDD: Caviar Blue 1TB $90
http://us.ncix.com/products/?sku=58881&vpn=WD10EALX&manufacture=Western%20Digital%20WD&promoid=1058
Mionix Naos 3200 $55
http://www.amazon.com/Mionix-Naos-Wired-LED-optical-Mouse/dp/B0041SPG24/ref=sr_1_1?s=electronics&ie=UTF8&qid=1336014125&sr=1-1
A nice mouse really does feel great, even for non-gaming tasks.
Total: $802 AMIR, which leaves you $15 or so for cheapo speakers, $5 or so for cheapo keyboard, and $130-180 for a monitor.
Obvious ways to spend more money:
Get the overclocking configuration (+ $85)
Get a 560Ti or better video card (+$50)
Get a better monitor, keyboard, or headphones.
Obvious ways to save money:
Drop to an i3-2100 or 2120 (dual core w/hyperthreading vs the i5's quad-core without hyperthreading (- ~$85)
I recommended the i5 in the main board, but the i3 is a very good budget option with combined with the H61 board above, cheaper than the AMD quad-cores + mobo.
Drop the SSD and deal with ordinary load times (- $125)
Use a **** mouse (-$50)
I did not budget in windows (a problem, particularly if he doesn't want to use the windows 8 preview, or a desk & chair. And as ironman noted above, you can get a good deal on a CPU at a microcenter... IF you want to drive out to orange county.
Edited by MisterFred - 5/2/12 at 8:30pm