Build me a $1000-$1200 gaming PC

Do you already have a monitor, keyboard, mouse etc?

Anyway, here we go.

Motherboard, Asus P5Q pro, the best for single GPUs. $115
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

PSU: Corsair 550W, $97
http://www.newegg.com/Product/Product.aspx?Item=N82E168...
There is also $750W for 10 bucks more, only useful if you plan to Crossfire in the future.

CPU: Intel E8400, $165
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

RAM: Mushkin 4gb DDR2 800 5-4-4-12 $60
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

GPU: Sapphire HD4870 512mb $250
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

Case: Antec Nine Hundred, $110
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

HD: WD6400AAKS (Western Digital 640GB) $75
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

Optical Drive, Lite-on SAT DVD burner $24
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

Total is $896.
That leaves enough room for Monitor, keyboard, mouse and anything else you might need.
Notice if the budget is $1200 and you don't need a monitor then the only worthwhile upgrade would be to change the motherboard to:
Asus P5E for $200 (+$85 from previous choice)
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

The PSU to Corsair 750W for $109 (+$10 from previous choice)
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

And the GPU to HD4870x2 for $509 (+$250 from previouc choice)
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

Bringing the total to around $1250.

Also one last thing, if your monitor is 24" or you plan to buy an 24" monitor (1920x1200 resolution) then change the first GPU to the 1gb version for $290
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

If I personally had $1,000 - $1,200 for a gaming build, this is what I would buy:

Intel Core 2 Duo E8500 Wolfdale 3.16GHz 6MB L2 Cache LGA 775 65W Dual-Core Processor - Retail
http://www.newegg.com/Product/Product.aspx?Item=N82E168... $189.99

GIGABYTE GA-X48-DS4 LGA 775 Intel X48 ATX Intel Motherboard - Retail
http://www.newegg.com/Product/Product.aspx?Item=N82E168... $224.99

G.SKILL PI Black 4GB (2 x 2GB) 240-Pin DDR2 SDRAM DDR2 800 (PC2 6400) Dual Channel Kit Desktop Memory - Retail
http://www.newegg.com/Product/Product.aspx?Item=N82E168... $59.99

Antec Nine Hundred Black Steel ATX Mid Tower Computer Case - Retail
http://www.buy.com/prod/antec-nine-hundred-steel-atx-mi... $94.99

Corsair TX CMPSU-750TX ATX12V & EPS12V Power Supply - CMPSU-750TX
http://www.buy.com/prod/corsair-750w-tx-series-80-plus-... $103.74 -$20.00 MIR

Western Digital Caviar SE16 WD6400AAKS 640GB 7200 RPM 16MB Cache SATA 3.0Gb/s Hard Drive - OEM
http://www.newegg.com/Product/Product.aspx?Item=N82E168... $74.99

SAPPHIRE 100259-1GL Radeon HD 4870 1GB 256-bit GDDR5 PCI Express 2.0 x16 HDCP Ready CrossFire Supported Video Card - Retail
http://www.newegg.com/Product/Product.aspx?Item=N82E168... $299.99

XIGMATEK HDT-S1283 120mm Rifle CPU Cooler - Retail
http://www.newegg.com/Product/Product.aspx?Item=N82E168... $31.99 -$10.00 MIR

XIGMATEK ACK-I7751 Retention Bracket - Retail
http://www.newegg.com/Product/Product.aspx?Item=N82E168... $8.49

SAMSUNG Black 22X DVD+R 22X DVD-R 16X DVD-ROM 2MB Cache SATA 22X DVD±R DVD Burner with LightScribe - OEM
http://www.newegg.com/Product/Product.aspx?Item=N82E168... $27.99

Total - $1,117.15 - $30.00 MIR's = $1,087.15

What resolution will you be gaming at? The above build assumes 24" and leaves the option for adding another 4870 in full-speed crossfire in the future. You could also go with a P45 chipset motherboard and 4870x2 if you don't think you'll want to do crossfire.

GIGABYTE GA-EP45-UD3P LGA 775 Intel P45 ATX Intel Motherboard - Retail
http://www.newegg.com/Product/Product.aspx?Item=N82E168... $136.99 -$20.00 MIR

VisionTek 900250 Radeon HD 4870 X2 2GB 512-bit GDDR5 PCI Express 2.0 x16 HDCP Ready CrossFire Supported Video Card - Retail
http://www.newegg.com/Product/Product.aspx?Item=N82E168... $519.99

Don't forget a 64-bit OS.

Microsoft Windows Vista Home Premium SP1 64-bit English for System Builders 1pk DSP OEI DVD - OEM
http://www.newegg.com/Product/Product.aspx?Item=N82E168... $99.99

Yes I already have a monitor, keyboard, mouse, speakers. I just need the computer itself.

Thanks a lot for your input!

+1 for shortstuff_mt's list.

Try to decide if you're more likely to want that second HD 4870 than not. If yes, it's more cost-effective to get the GA-EP45-UD3P/HD 4870 X2 combination than to do Crossfire. Think of it this way: $225 for the GA-X48-DS4 + $300 for HD 4870 1GB + (guessing) $200 for a second HD 4870 1GB a year from now, you end up paying $725 and you don't even get the full performance for the first year. With the GA-EP45-UD3P/HD 4870 X2 you pay $117+$520 = $637 and get the full speed right away.
Also check out these products:
NZXT Tempest $90
RC-690 $75
Silencer 750W $110 - 15%

okay where do you live? ill meet you and help you build it