What are some things only an idiot does when in the gym?

idiot n.  1. Psychol.  A mentally-deficient person, with intelligence in the lowest measurable range.  2.  A stupid person or fool.  

The following are things I've witnessed knuckleheads do when in the gym that make me either cringe, laugh inside, or consider first-class entertainment when in the gym environment:

• Lifting too much weight at the expense of good form
• NOT re-racking weights (!)
• NOT replacing weights in the appropriate place (!)
• NOT allowing enough room in front of the weight rack for others to walk when lifting (!!)
• Dropping the barbell onto the floor when deadlifting (!!!)
• Performing incessant ab crunches as if that's all that's needed to obtain a 6-pack
• Leaving free weights unattended at a bench
• Leaving keys and/or water bottle and/or towel at a bench and working out elsewhere (!!)
• Hovering near a weight bench without using the bench (e.g., performing standing barbell curls near a bench)
• Walking around the gym puffing the chest and invisible lats
• Performing the same routine over and over and over again with nary a change to the physique
• Performing barbell curls at the squat rack
• Spending way too much time talking on the phone or incessantly checking text messages between sets
• Bouncing the barbell off the chest when bench pressing
• Lifting the legs up when bench pressing
• Leaving 10 plates on the leg press machine
• NOT squatting to parallel 
• Squatting 400-lbs for a 5-inch range of motion
• Wearing jeans and/or flip flops
• Leaving sweat on any piece of equipment when done
• Dropping dumbbells onto the floor at the end of the last rep (!!)
• Grunting way too loud when lifting
• Preening in front of a mirror
• Excessive body odor (and this is before the workout!)
• Doing ridiculous balance exercises with a stability ball, a Bosu ball, a flex band and a medicine ball--is this really necessary?!
• Chatting incessantly (often with a hot girl) rather than working out--save the socializing for outside the gym!
• Performing quick jump roping on a mat, creating a loud nuisance
• Jumping on and off of a treadmill which is going at a high rate of speed (Believe it or not, I actually saw this.  Is this really necessary?!)

I'm sure this list will grow, perhaps almost every day, as I witness the pitiful inanities within the walls of the gym.  Ah, humans are mighty entertaining indeed.