Unnecessary advice
I think it's funny (and stupid) when advice consists of phrases like "just breathe".  I hear it in sports a lot, and I know a girl who got it tattooed on her wrist.  What's the alternative?  "I think I'll hold my breath until I pass out."  You don't need to say it if it's literally an unconscious function of the human body. 

The same goes with advice about drinking water.  It used to be accepted common knowledge that drinking [X] cups of water a day performed some vital function for your body.  But then the experts changed their minds about that quantity when people realized drinking more water provided no measurable benefit.  How about this advice:  Drink when you're thirsty.  That's it.  Why do we need to make this more complicated?

Footprints in sand
I've noticed that my brain, in the presence of alcohol or allergy medication that causes drowsiness, tends to retain information similar to footprints in sand getting washed away by the waves.  The imprint is still there, but the full context disappears.  I'll have entire conversations or read chapters of books, only to think back on it and simply recall that the activity happened, not the information contained therein.  This can be bad because I might say things I don't remember, and then get called out for saying something dumb.  But it can also be good because people talk too much, and I don't need that stuff clogging up my processor.

Big internet things
I'm consistently surprised when things that appear to be in the collective conscience of society still haven't quite crossed the threshold and instead remain in relative obscurity.  The easiest example is any video from YouTube that has more than say 100 million views.  Ask the average person if they know what the fox says, and chances are they won't know what you're talking about.  Granted, a lot of this depends on your view of the average person.  If you're a teenager, your view of "average" is probably one of your teenage friends.  While in reality, average is probably a 40-year-old white mother from Ohio.  Regardless, there seems to be a delay or an impediment between certain things gaining widespread notoriety (e.g. Gangnam Style) and other things remaining popular but not universal.

Circle of poop
Rabbits eat some of their own poop, sort of like how cows chew cud.  It seems weird, but it's not only normal, it's essential to their survival and their bodies depend on it.  Whenever I see my rabbit eating his poop, I say it's the circle of life.  Which is funny, because that's not what that means.

Reddit, I get it
I've known about Reddit for a long time now, and I've browsed it on occasion but was always overwhelmed by the frequency of updates and sheer volume of content.  But just recently I figured it out:  Reddit's value lies in its user base.  The website is simple enough:  It's essentially a forum where users post things and other users comment.  One of the things that helps the community at large is the ability to upvote and downvote each and every comment, as well as the nested comments that make it more of a discussion.  But by far the most important aspect of Reddit is that its users tend to be a little more intelligent than the average internet citizen.  There are still childish comments and personal insults, but there's also deep insight and links to information that backs up opinions.  Instead of a typical web forum, Reddit is like a web forum of people you know, or at least people you'd like to know.  There's personal depth, sort of like real life.  It's really cool stuff, and I'm surprised it took me this long to figure it out.

Sports injury reporting language
Something I've noticed for a little while now is how injury reporting during and after sporting events uses strange language.  They say things like, "This person is out with a hamstring," or "Coaches say that person is dealing with a shoulder."  The "injury" part is implied, but it still sounds weird to me.

Crack mayor
The mayor of Toronto admitted to smoking crack while drunk, and this was apparently a sufficient excuse in his mind.  I've tasted alcohol.  I've experienced some of its effects.  I've done things I've later regretted while under its influence.  But I can't say I've ever done any drugs (or committed any other felonies) and passed it off as an acceptable by-product of alcohol-impaired logic.

Thermoelectric effect
An Ecofan is a small metal fan that sits on top of a wood stove or other heating element and provides low-speed air movement to aid in spreading heat around a room.  It literally generates its own electricity via the thermoelectric effect, which is a well-understood method of generating voltage with a temperature difference.  It's essentially magic, and it's awesome.

Euler's identity
Euler's identity is a mathematical equation that goes like this: 
e + 1 = 0
The reason this is significant is because it's a simple equation that contains five of the most fundamental and important concepts in math.  See?  Math is purdy.