For me it's probably either

• the Dell Dimension that was Everybody's Windows 98 PC. That one's only special to me for sentimental reasons being my first PC, ever
• an I think HP? Not entirely sure off hand, that has "ME" written on it in sharpie and gives no signs of life, I suspect due to bad capacitors somewhere and/or a bad PSU, or
• the Dell Optiplex GX something or other that was my grandmother's. It's known to have bad capacitors and give no visible signs of life, and supposedly it wasn't good when it was new, but it's at least funny for having a "designed for Windows XP" sticker and a Windows 98 SE product key