You can choose to fail saves. If you can take 10, a GM would probably let you take 1 as well, depending on the situation. Though, if you wanted to look like you were actually trying but failing that might call for a bluff check.
What are you trying to do with it?
What are you trying to do with it?
I can't speak for the OP, but I know I've wanted to fail rolls to confirm critical hits.
There are abilities that have you attack your friends. If you could simply say "sure, I'll just roll a 1 and miss", those abilities would be rather worthless.