Common phrases for something that appears good but is actually bad

What are common phrases that describe something that appears good but is actually bad?

Edit: Because people say bad is vague I will try to sum up the phrase meaning a little better.

• something that looks like it will be helpful or advantageous but after use it is hindering

• a tool that seems useful but is not the correct tool for the job

• something that seems like a good idea but after execution turns out to be problematic

A poisoned chalice is something which seems good when received but actually does great harm.

If you want a proverb, it could be "Not all that glitters is gold", although what is not good is not necessarily bad. Perhaps a good expression could be "a wolf in sheep's skin", as this is exactly a bad thing disguised as good.

The term that pops into my mind is "Fool's gold", after the mineral Pyrite, which looks like gold, so deceives those on first inspection.