bayoubill
For me that would be Young Rascals

Bill, Just curious. What didn't you like about the Young Rascals? They put out some great tunes. I have never seen them live, so I cannot comment on my own. I guess I would just hope that they were good.  

U2. Probably didn't help that I had the worst seats in the venue (literally TOP row in the upper upper bowl) AND Kanye West opened for them.
 
That was the one and only time I let a friend get the tickets. 

Smashing Pumpkins.
 
I went to see Marilyn Manson but had to stay for Pumpkins afterwards. I never particularly liked them, though I dug a few songs.
 
Not only was Billy Corgan's voice even more unbearably annoying live, but they played mostly long, atmospheric jams - and the Pumpkins aren't exactly playing on the same level of musicianship as your average prog rock band, so... Basically, 2 hours of agression on the senses.
 
I got out of there feeling like I needed to hit someone. I couldn't even stay for a drink with our friends afterwards.

I only walked out of one concert. Nelly Furtado. To this day I'm not sure why I went. I did not even list her in my "saw" category. That's how much she sucked for me.
 
OK, bring on the suck jokes.

bapu
I only walked out of one concert. Nelly Furtado. To this day I'm not sure why I went. I did not even list her in my "saw" category. That's how much she sucked for me.
 
OK, bring on the suck jokes.

The other side of this experience.  I was at a fancy restaurant after the Canadian Music Awards one year, and she showed up with her awards and a huge entourage.  The restaurant refused to seat her due to the number of people, and her rude response.
You walked out, she walked out.  
 
Oh, and she didn't get to suck so much as a Pepsi.

I'm sure I have at least one for this list, but my 'automatic eraser of bad memories' function is working well. 

Michael Ball. 2 hours of utter middle-of-the-road tedium. The things we do for the wives.

Like Bapu, I didn't list this band in my have seen list because it was soooooo bad. At least I don't think I listed them.
That band would be Bon Jovi.

I went to the Who's farewell tour. IF somebody had told me there would be 10 more farewell tours I would have saved my money.

Allegedly The Drifters, on some package holiday night out in Spain.