Long silence, often used in response to a stupid question.

blank stare used in texting or email, typically to portray a feeling of disbelief, frustration, or impatience

A series of 3 periods that, like the word "Hmm" can be used as a space filler during an awkward silence. However, they are also used to create suspense for usually unimportant situations, to answer a stupid question, counter a stupid comment, or simply to piss people off because of overuse.

triple dot of awkwardness

used in texting
a way to say that you're not really sure, or lets just not talk about it

Mainly used in chat rooms or forums, in response to a sentence or phrase which cannot be replied to in any other way because it is incredibly stupid or strange.

Also known as an ellipsis, usually used to represent a word or phrase necessary for a complete syntactical construction but not necessary for understanding.
1) Often used at the end of a written sentence to denote trailing off See Yada Yada Yada
2) Used in response to a (written) incomprehensible statement or a rhetorical question