¿Dormimos juntos?

dormir - (verb) to sleep
juntos - (adj) together

I love this one. This particular phrase is easy to translate directly into English. It asks the question "did we sleep together?" in a joking fashion. Here is an example of when you might use this phrase: Let's say you go to your local bar after work for a drink. You happen to see a friend there, but he or she does not acknowledge you or greet you in the proper way. In a sarcastic and joking tone, you would then say to your friend "¿dormimos juntos?", and you would both laugh about it. Confused? So was I the first time this phrase was explained to me. Ok, so the first thing to understand is that in the Latin culture, greetings are given much more importance than in the United States (maybe it's just in LA). If you see a friend or acquantaince in Colombia, you typically show respect by giving a proper greeting... handshake, hug, kiss, etc. So if your friend at the bar does not greet you properly, it is seen as disrespect. Here comes the joke: You would then say to the friend "did we sleep together" as if you woke up together, and already gave that person a proper greeting that morning. So you're seeing them again, later in the day, and can offer a more relaxed greeting. This is a great Spanish joke that I wish could be used in American culture. Of course, asking someone "did we sleep together" at a bar in the States will likely get you punched in the face.

Aterriza

aterrizar - (verb) to come back to reality, to stop dreaming.

I learned this one from my mother-in-law. If you're acting like you've got your "head in the clouds", one might say aterriza!, or "come back down to earth". I would guess the root of the word is derived from the Latin terra, which directly translates to "earth". I hope I don't hear this one too much from my mother-in-law... or my wife for that matter.

[wiktionary]

Tacaño

Tacaño is a Spanish word that means "cheap" or "stingy". The great thing about this word is that you get to use a special hand gesture along with it (as shown in the picture here). You basically make a fist, and then hit your elbow with your other hand. I think it's supposed to mean that your fist is holding money, and you're trying knock out the money with the other hand. Be careful, however, as this is very similar to an obscene gesture called the bras d'honneur, where the only difference is that your bottom hand goes on the inner part of your elbow. If you call someone a "tacaño" and then use this incorrect gesture, I can promise you there's gonna be trouble.

Limosnero y con garrote

limosnero - (noun) beggar, panhandler
garrote - (noun) chain, whip, or club

The most direct translation of this term is "beggar with a club". This, of course, means nothing in the United States. However, once you hear the explanation, you realize it is very similar to the English saying "beggars can't be choosers". Definition: If someone gives you something you asked for, you should not complain about what you get. The Spanish term simply uses more colorful language. The "beggar" in this case is not just complaining, but he's using a chain in order to demand what he wants. I much prefer the Spanish version in this sense :)

[Beggars can't be choosers - TFD]
[Limonsnero y con garrote - Word Reference]