I thought it would be fun to start a threat where we help each other solve the mystery of half remembered books, the ones you may want to read again but have no clue what the title was.

Try and put down as much info as you can: words that may be in the title, dates you read it or it may have been published, genre, etc.
I'll start:
1. I read this somewhere between '03-'05. It was either strait SciFi/Horror or YA Scifi/Horror. It took place in some big city (don't remember if they mentioned a name or not, seemed to be in the eastern US). Followed groups of what I think were werewolves and they would roam the city in packs, each pack had a leader. Some characters worked/hung out at a bar, one (I think antagonist) was named "Tanzer" and near the end of the series, one or two characters die and they go to a spirit world where something is hunting them, the "something" might be able to cross over. It was violent and had some language.
2. Dean Koontz novel I read a few years ago. A brother and his autistic sibling (whose wardrobe consists of multiple pairs of shirts with the same cartoon character) become involved in some weird experiment/phenom on. People and objects can teleport, but every time they do pieces end up in the wrong place (fabric from your pants end up on your shoes, etc) and people get gradually sicker the more times they do it.
3. Another Dean Koontz, all I remember is a young man with Downs Syndrome (sibling of the main character) would call butterfly's "Flutterbys".