Da

Da - noun/pronoun
It is a well-known word found in the lexicon of tamil and malayalam population (of other languages I have no idea da). Its a versatile filler, a universal prefix, and an unavoidable suffix in most conversations. This two letter 'biggie' is the most popular word owing to its flexibility to be used in different situations and connotations with just slight variation in tone.The fact that almost 80% of any meaningful conversation consists entirely of this commonplace term speaks volumes about  the popularity this word enjoys.
The common versions are shown below.    
1. Da! (may or may not be followed by expletives): When delivered like a pop of a bullet with a slight dent in teh tone; expect a punch from the speaker. It is the intimidating da. I have come across this only in Kerala.
eg : da @##%^&@@*! give my money back!

2. Daaaaaaaaaa ( when delivered lazily with the dreary voice dying down in time) : The speaker is searching for an excuse.
eg :Daaaaaaaa! I forgot to  book your ticket to the U.S daaaaaaaaaaaaaaaaaaa

3. Da (delivered mostly in a husky voice) : the cajoling da. If uttered by your better half get ready to be robbed of all your money.
eg : Da(heavy breathing) can we go for shopping today?

4. DaaAAaa : A variant of the above. Also used to lure an innocent listener into something. Characterised by the speakers voice travelling to the upper  octaves and coming back.
eg :  Come on, lets kill this guy  DaaAAaa!

5. The above can also be used to tease a person after he has done something embarrassing or unspeakable
eg : DaaAAaaa ! Did you vote for Congress ? Shame! Shame!

The other variants include the cracker da which is in fact a series of da delivered one after the other(da da da da) resembling a drumbeat used mainly to intimidate a person; the revelation da which is a da in the form of a shriek usually used after you discover who stole your rare medival period coin from your collection etc.
Da can also be used to mark the end or the beginning of a statement or used as meaningful pauses fixed in between apologies. New forms and usages are being introduced every second.
The list is endless , ever growing and evolving da.