1. To 'take a real one' is to have a bowel movement that is particularly forceful or emotionally necessary. The feelings that accompany 'taking a real one' are typically frustration, surprise, and/or anger. To 'take a real one' is to figuratively unload a pile of feces onto a situation which bears no other possible reaction. 'Taking a real one' also implies that you can't even mentally just imagine crapping on something, you are are so annoyed that it is literally forcing a big load of pants-pudding from your agitated lower intestine.
2. Oh for the love of Pete! I just lost my entire thesis. Thanks a lot Microsoft Word! This makes me want to take a real one.
3. For the entire movie, all I could think about was taking a real one.
4. I'd prefer to take a real one rather than stay at this bar for another second.