Irony is one of the most misunderstood things in the English language. Even Cracked got it wrong once. Hell, I might even be wrong...fuck it!
This irony is the one that causes the shitstorm of commotion. It is often misused, and is often deemed interchangeable with sarcasm. While verbal irony and sarcasm are similar, they can not completely replace one another in some situations. The only difference between the two is that sarcasm is direct, and is intended to be caustic and insulting. Here are Merriam Webster's Definitions of the two:
Verbal Irony (under Irony): n. - the use of words to express something other than and especially the opposite of the literal meaning.
Sarcasm - a sharp and often satirical or ironic utterance designed to cut or give pain.
Notice how sarcasm's definition contains the word ironic. Wait...it gets more fucking complicated. Sarcasm is actually just a subtype of verbal irony. There is sarcasm, overstatement, and understatement. Sarcasm is the most used...as 100% of human beings are professional smartasses. Here is an example. Say you see Mickey Rourke in a club. You walk up to him and say "Gee, Mickey Rourke, you're sure looking not ugly and haggard these days!" That's sarcasm, as you're saying the opposite of what you mean, and also are hurting Mickey Rourke's feelings, prompting him to kick your ass.
You go home and your wife says, "What happened?" You respond "Mickey Rourke killed me." Congratulations, you've used an overstatement. An overstatement is an exaggeration of what the reader said, making what he actually meant seem a lot more ridiculous. In contrast to that, you have an understatement. Say you wife asks you why he killed you, and you tell her it's because you told him "Your face looks like a horse's ass." What you initially said to him would be an understatement, since horses asses are way more attractive. (Mindfuck alert) There are also things called Litotes where you're supposed to negate the contrary of something. Example: "She's not bad in bed." ==> "She's quite good in bed." Fuck it, just stick to sarcasm.
There is also Socratic Irony, which is used to simply describe that you're a jerk who ultimately wants to call someone out on their lack of knowledge (of which I'm totally doing with this article). Socratic irony means that you ask someone a question, pretending you have little knowledge, when you actually know more than the person you're asking.
No one gives a shit about Dramatic Irony anymore, unless you're a Harry Potter or some other fictional book franchise fan. As previously mentioned, dramatic irony is where a character is unaware of his fate, whereas the reader is fully aware. If the characters in the book knew they were in this situation, they'd probably kick your ass for not telling them.
Ah, the most hilarious, misunderstood and arguable type of irony. Situational irony can be described as when something happens that is contrary or incongruent to what someone expected to happen. As a certain other article stated, this is often confused with a coincidence or an obvious chain of events. Here are some examples of each.
Coincidence - "Hey, this guy next to me ordered the same drink I did. How ironic." No, it's not. It is a fucking coincidence.
Obvious chain of events - "My ex boyfriend was a real jerk, turns out he was on steroids. How ironic." Again, fuck no it ain't. This is just an obvious outcome of an obvious cause. Shut your hole.
Situational Irony - "I just found a fire extinguisher that shoots fire. How ironic." Good job. Nobody would have expected this to happen, so it was indeed ironic.
Situational irony also gets commonly dismissed as bad luck. For example, you're at a bar and decide to try to hit on this Japanese chick. Little do you know, she's in the Japanese mafia and ninjas jump out an ninja star the shit out of you before you can say "Nice ass." It's unlucky, but it's also ironic because you couldn't have seen it coming and it makes no fucking sense.
Let's take a look at some pictures and discuss in detail if they are ironic. Most of these can be found in a certain other article as counterexamples of irony.
OK, the facebook page up there is a little bit counterproductive. This is, in fact, irony. As stated in that page, though, it is because you would expect kids to eat ice cream, not ice cream to eat humans.
This one is arguable. If you would expect scientists to play with toys, which you wouldn't, this would be ironic. One would assume that he would at least use a computer instead. However, if you're like me, a scientist who DOES play with toys, then it's not ironic. To the rest of you who still have brains, let's continue.
Another gray area. You would expect them to be fighting a real war, not one with plastic...so therefore it could be ironic. However, military dudes playing risk is a little too appropriate. In other words, if they did play board games, this is definitely the one they would play. If they were playing a board game called "Peace and Hippies" then it would be unquestionably ironic.
This one would be ironic if you saw the caption before you saw the picture. However, since there are boobs in the picture, that would be physically impossible as is. You would have to post a link to this picture with the same caption...then it would be ironic.
Bad excuse for a demotivational poster? Yes. Irony, no. Nothing unexpected happened here...plenty of idiots on the internet and one was bound to make a blatant spelling error eventually.
Here is a quote, thanks to George Carlin and Cracked user Tedwild that also shows that irony is scalable and can be distorted dependent on the situation. "If a diabetic gets hit by a truck and killed on his way to buy insulin, that is not ironic. If he gets hit by a sugar truck, that is mildly ironic. If he gets hit by an insulin truck, that my friend, is irony writ large."
As you can see, irony can be distorted to conform with a particular person's point of view. If the person is normal, and many hilarious things are unexpected, then everything is ironic. However, if you're far too imaginative and think that ice cream overlords exist and will lick our heads off, then go get help. This more than likely contributes to the world's opinion on irony, so those who don't understand it have good reason. However, PLEASE stop using it to describe appropriate or obvious situations. Just...stop.