My best presentation at university was during a small seminar. It was a 45min talk about 3 papers and how they relate to each other. I procrastinate a lot, so I didn't really do anything besides reading those papers until the day before my presentation. That day, a friend called for a spontaneous barbecue, so I had just an odd hour to actually prepare slides. I managed 8 slides in total, the rest I just impromptu recalled from memory. People liked it and it was the least effort I put in any talk I held at university.