Never heard it pronounced as anything other than asterisk with both s’s sounded and all 3 syllables.
I’ve heard the symbol called something entirely different (star, splat), but usually not in a serious context.
For pronunciation aid, I just remember the quote, “I have only one asterisk for my country”. 
I’d like to axe how people who say asterick or asterix axe people questions.
I pronounce both S’s; Midwestern US.
BTW, that pronunciation is the only one that makes this poem make sense:
Pretty Mary bought some skates
Upon the ice to frisk.
Wasn’t she a silly girl,
Her little * ?
How do you feel about the fact that there are two “r’s” in “surprise?” 
I also pronounce it with both s’s. It’s an awkward word, but you gotta do what you gotta do.
My time spent in NE each year cured the pop right out of me. I was the only one of my friends who said soda.
I also now pronounce both S’s, but before I knew that was correct, I said astriCk with no middle e. Texas.
I say asterisk. Born in NW IN, now living in IL near Chicago.
I have never heard anyone say asterick. If I HAD ever heard it spoken this way, I would make an assumption regarding the caller’s literary intellect. The same way I do when people say nukular or pronounce every syllable in com-for-ta-ble.
I say asteriSk. Born and raised in the South.
However, around here I have heard many common corruptions of it, including asterix, asteric, axterix, and axterick. It’s hard for some folks to pronounce.
By misspelling it every time. Thanks, spell check.
Also, February.
I never knew anyone pronounced it asterick. I thought it was either asterisk or asterix. You know, like the word ask.
I honestly don’t find asterisk hard to say at all. I do find February hard to say: if I try to say it “correctly,” it comes out Febrrrary. So I tend to stick with Feb-YOU-airy.
Uh… northeast or northwest? Parallel linguistic universe?
Really, all the people from here that I’ve asked leave out the second s.
Same here.
Northeast. Though I will qualify that I’ve never actually made an inquiry about it, and it doesn’t really come up in conversation frequently.
AsteriCk, usually, but I’m aware it should be -iSk. Grew up in KY if it matters.