PUT YOURSELF TO THE TEST. (NSFW-ish.)
1. You have to read the whole post.
2. You must not giggle, not even once, because you are an adult.
3. You cannot smirk at all, because you are a grown human person with a not-at-all sophomoric sense of humor.
4. No laughing! You are not 12!
5. Ready? Let's go!
OK! Let's start with some run-of-the-mill business signs.
Source: mulchthief
Source: i.imgur.com
This sign is totally not funny.
Source: ouchoutrageousobnoxiousandodd.blogspot.com