Maybe not dead, but a video card or CPU could have been abused -- overclocked too high, overvolted, run without proper cooling.
A video card or motherboard might have a bad BIOS flash attempt.
A video card or motherboard might be missing manuals, drivers, cables, adapters like DVI to VGA, mini-HDMI to full HDMI, or the I/O shield for the case. If a video card normally comes with a game code it may be gone or already used.
If the bare card is all you need then maybe it's worth the gamble if the price is low enough,