I'm going to go with the XBox and the PS2. The PS2 isn't super ugly per say, but in an industry that had already produced the Duo R, the DC, the PS, the PSOne etc there is no excuse for something that shitty. The Xbox is just garish and hideous and terrible. Shaped like a giant X with a bunch of neon green on it. Wow. Lame. Straight into the hands of people who collect CDi, Jag and 3DO and insist that the games aren't "that bad" when in fact they are the worst ever.
Its amazing that anyone could think the Wii is ugly. It doesn't look like much of anything, and its small. Ditch the vertical stand and it pretty much just looks like an external burner...only smaller. I can see people saying its too cautious or boring, but there isn't enough character there to make it ugly.
The Famicom is rather ugly in itself, but at this point I'm extremely nostalgic for any 1980s era white plastic from Japan. Little keyboards and databank calculators and stuff.
As far as bootleg systems, I have a "Handy FamiEight" or something like that which is hideous.