Evil powerpoint slides.
Multiple shots of that animal or flower you saw during your vacation, that yes, while interesting, does not need more than one slide in your talk.
Non-mocking, gratuitous product placements.
Being under the influence.
Slides depicting graphic surgical techniques (unless of course, your talk is about the said graphic surgical technique).
Intense body odor.
The font: Comic Sans.
Wearing sunglasses for no apparent reason.
Not making eye contact.
Your phone ringing.
Significant use/exploration of body orifices.
Poor colour choice on slides.
Sub optimal body fluid control.
Being too long.
Losing your dentures.
Excessive slide animations.
Revealing, distracting attire.
Apparent and/or perceived randomness.
Overt, uncalled for arrogance.
Laser pointer abuse.
Embarrassing computer desktops (during setup or slideshow problem).
Not having a backup.
Being an idiot.
Thanks to PhysioProf, Karen, Chris, Jenjen, Stephen, Janet, Fiona, fizzchick, Tara, GrrlScientist, 6EQUJ5, Eva, Timon, RPM, John, Mark, Cherish, bsci, tguy, HP, tk, le.gail.savant, Feynmaniac, Matthew, Mike, Lab Rat, George, Eric, cowgirl, Mike, Eric, Samia, and Lisa. To suggest more, please go here and leave a comment.