When a moment or memory that is fantastic, requires a better word than funny; but you don't want to sound dumb by continuously adding so's in front of it. (you know you've been in this situation before)
Also needing a better word than hilarious.
Can also be used in replacement for the word insane, but only on rare, necessary occasions.
Oh my god! That day was so freaking SANIC!!
I like that guy, he's totally sanic.