You have eight billiard balls. One of them is "defective," meaning that it weighs more than the others.

I think I figured out the billiards one, but I don't want to give you the answer straight out.

Here is a hint, you don't have to weigh all of the balls the first time.

Also, make sure you draw this out on paper, it makes figuring it out a lot easier.

Did you actually figure out a way to get 100% accuracy?

I've managed two system of 75% accuracy, but nothing giving 100% chance of success.

Weigh the balls this way:

3 on the left and 3 on the right.
If neither side goes down, then your ball is one of the remaining two, which leaves only one weighing in left.

If not, then one side will sink.
Take those 3 balls, and toss the others out of the equation.
Weigh 2 of them on your second weigh in.
If neither side sinks, then the odd one out is your man.
If not, then the choice will be obvious...100% of the time.

The pills are a little tricky...I'd think outside the pill bottle.
But do you really have to constrain yourself to using a scale?

here's a little doodle for you...