Homeopathy.
The average remedy is 30c, which is 30 to the power of a hundred.
That's the equivalent of one ml of 'active' ingredient diluted in an Olympic sized swimming pool, bottled up and sold.
If you are going to argue from a scientific point of view, then its important that you get your facts and number right. 30C means 100 to the power 30 (=10^60), not 30 to the power 100 (= 10^147).
While you've significantly overstated the dilution of 30C, you've significantly understated the diultion with the swimming pool comparison. At 30C, 1ml of active ingredient would be diluted in 10^57 liters of water, or the same amount of water that is in:
400,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000 olymic sized swimming pools.
Putting it another way, a 30C solution would contain one singe
molecule of active ingredient in:
10,000,000,000,000,000,000,000,000,000 olympic sized swimming pools of water or
20,000,000,000,000 times the entire amount of water on earth.
Or even another way. In any one dose of 30C homeopathic 'medicine', the chance of consuming the active ingredient is the same as the change of winning the lottery every single week for:
30,000,000,000,000,000,000,000,000,000,000 years.
No mater how much of a 30C solution you consume, you will never drink the 'active' ingredient.
The homeopathic response to this is to say that there is some scientifically unkown mechanism by which water takes on the characteristics of the 'active' ingredient. I think Tim Minchin answered that best in his poem 'Storm':
It's a miracle! Take physics and bin it!
Water has memory!
And while it's memory of a long lost drop of onion juice is Infinite
It somehow forgets all the poo it's had in it!
And to all the people who say 'well it worked for me, how do you explain that?' - the plural of anecdote is anecdotes not data.