In my opinion, a couple stand out:

Memorex VIS. The VIS tried to compete with the Philips CD-i, and failed miserably. Let's put it this way: the Genesis and SNES put together sold 84.35 million units. The CD-i sold 1 million units. The VIS sold 11,000 units!

The CD-i sold about 1.19% as much as the Genesis and SNES combined; the VIS sold 1.10% of the CD-i! That means the VIS was a bigger flop compared to the CD-i than the CD-i was to the the two main consoles on sale combined when it was released. The VIS had no redeeming value, it was slightly cheaper than the CD-i and that was about it. It also had only about 50 titles available, most of those were garbage-quality "edutainment" titles, few real games. Not to mention it had an Intel 286 processor, which was common in computers in the early-mid 1980s... but this was 1992! At least the CD-i had a few good games like Burn:Cycle, Voyeur, NFL Instant Replay, etc. Those 11,000 units include a number of VISes sold for $99 with 30 titles included in 1994. Keep in mind, the VIS was $699 just two years earlier.

Jaguar CD. Was there any reason to get this thing? The cart Jag didn't have much going for it, but it at least had a handful of good games and exclusive titles, and it was a solidly built system. 13 games, 2 of which came out over a year after the system ceased production (so we're down to 11), 6 of those were ports available on other, much more common systems (all 6 were available on MS-DOS PC's, and most people in 1995 had an MS-DOS PC), we're left with Baldies (which came out for PS1 but eight years later), Battlemorph, Blue Lightning, Highlander, and Hover Strike Unconquered Lands. Battlemorph, Blue Lightning, and Baldies all got decent but not great reviews, Hover Strike UL was okay, and Highlander was TERRIBLE. By the way, Blue Lightning was a graphically enhanced remake of a Lynx game of the same name and Battlemorph and Hover Strike were the sequels to cart Jag games. Not to mention the Jag CD was so unreliable it might as well have been made of paper. Only 20,000 were sold and I fail to see why one would buy one then, unless they were a huge Baldies fan and/or liked the way the Highlander CD looked as a drink coaster.
(If we're being nitpicky, the two games released in '97 after the Jag CD ceased production were sequels as well: one to a cart Jag game (Iron Soldier 2) and one to an Amiga game (World Tour Racing)... today leaving only Highlander as a true "exclusive". Then again, today the Jag CD is collectible based on its crap factor and rarity)