Chile is a long, thin country, ironically resembling a chili pepper (although they don't really eat peppers or spicy food here, sadly). Because of the distance between the population of the country, accents vary; and the large majority of my experiences have been in Santiago, so don't over judge or over analyze my commentary on the spoken word here.
Sipo
Chileans like to use "-po." It's attributed to a variation on "pues," and it's actually pretty cute. "Sipo" and "nopo" are pretty common words here (instead of the homely and simple "si" and "no"), but that has also morphed into the very common "yapo" as an affirmative, as well. Po is not limited to just yes and no responses. Chileans, especially when speaking casually among other Chileans, throw "pos" in there behind just about every word, and if you are speaking to a true Chilean, they throw "pos" in after English words, too. My favorite example of this is, "obviouslypo."
Palta
Avocados are plentiful in Chile, and they eat them on everything -- from hotdogs to burgers to bread. Avocados are prefered smooshed with a bit of salt, and possibly another Chilean favorite: mayonaise.
Nonetheless, avocado in Chilean spanish is not "aguacate," but instead "palta." I don't know where the change came from, but I guess the Andes caught the common word for avocado and somehow delivered "palta" to this lovely avocado-producing powerhouse of a country.
Speaking of the plentifulness of paltas, we have an avocado salesman at La Vega (vegtable market) who only sells palta, and we have been able to locate and purchase up to six different kinds of avocado in one trip.
Weon
So, using "juevón" -- or as it has changed over time to "weon" --is extremely common, but the word's meaning changes with how you use it.
I'm not going to go into the literal meaning of this word, but if you use it among friends "weon" or "weona" means something like "dude." Using it in a fight or in the car, the word has a much nastier meaning, and can be taken very badly.
Cachai
Chileans use a Spanglishism that I wish we had had in the Valley (capital of all Spanglish on my map): "cachar," which means "to catch."
In other words, "Did you catch that?"
In use: "El edificio está antes del semaforo, ¿cachai?"
Obviously the verb conjugates to "cachaste" and the like, but Chileans use it as a breather, like "po," and it's pretty catching.
Warning: Use at Your Own Risk
Nonetheless, I've been advised by my lovely Spanish teacher to refrain from using Chilean-isms, because I may not fully understand their implications and be taken the wrong way, which leads me to a story I know from one of my favorite Chileans I've met here:
My Chilean friend was on a work trip to Peru, where he was explaining how an IT system was going to work, pointing out different items on a work map to the woman client there. After everything he explained, he said, "cachai," as Chileans do.
Unfortunately, the verb means something completely different in Peru, and he was essentially mapping out a porno with the words he was using. Whoops!