Whoa, this thread is older than some people's kids on here. If you take the last 3-4 years or so you can make a strong top ten:

1- Phaze
2- Fight
3- Street Fight
4- Byte
5- Zero Gravity
6- Drive
7- Optimus
8- Optimus Solid
9- Reign-On
10- Fire Road

Those are ten off the top of my head that just had iffy reactions and were clear cover/core mismatches for the average skilled bowler. But if you throw it good and know how to read a lane, you can always find something that a "bad ball" would work on.

I shot 300s with the Byte, Zero Gravity, Reign On, FireRoad and 300/800 with the Fight lol

Wow! This is a pretty old thread! I always say, there are no bad balls just bad operators! But, there are a few turds out there as well.

For me:

1. The Shift
2. The Invasion
3. The Reign
4. XXX Extreme
5. The Fight (condition specific-needed oil, lots of it)

+1 on The Shift.  Sure didn't cry when that ball cracked.  Spoiled me on the brand for awhile but glad didn't give up on Storm and Roto though as love the Hy-Road, IQ Tour and Hustle Ink.  Have had some match up problems also with the Raven so it may be more don't match up well with particle balls.  Also as an unrelated aside only going to be on occasionally going forward so no more crap flooding posts.  Win win for everyone.

Invasion and VG Nano Solid= TURDS!!!!

Funny that you mentioned that Match-Up Pearl in your list. I know one bowler who plays a pretty direct line to the pocket and swears by his Match-Up pearl!! He uses it on a fairly slick medium shot, and is consistent with it. Lots of 220ish games with it.

However, this past Friday I bowled against a guy with a ton of hand, who insisted on trying to swing the lanes from about 25 to 10 with it.....and all he did was destroy the natural track area for all the down-and-inners bowling on the pair! Third game everyone trying to play down and in kept getting wash-out splits over and over again since he had pushed oil into the natural track area!

You'd  think he would have stopped since his ball NEVER made the turn to the pocket either.......BUT NOOOO! He kept right on trying to wheel it!

I literally had to go get a stronger piece and play inside of him in order to score!

Yeah, that Match-Up pearl is probably condition specific for sure.