For the life of me I can not say ‘peculiar’
I sometimes have difficulties with colloquial. I really don’t know why.
I’ve noticed many people can’t pronounce Authentication.
Despite the amount of Wodehouse I read, I still can’t pronounce “stentoriously” even in my head.
Saturday. It comes out as Sar-day, with the first syllable rhyming with ‘‘chair.’’ No glottal stop, just a skipped T. FWIW I’m from the Pittsburgh area.
Remuneration, Recidivism, Colloquial - I can pronounce them, but I have to do it slowly.
Rural, Rory - pretty hopeless.
Also Halo-halo, a Philippino dessert - the “a” sound is supposed to be somewhere between “hallow” and “hollow”, but I can’t get it right.
“Statistics.” Trip over it every time. Sta-stis-tics usually, though sta-tic-tics, sta-tit-ics, and other variations are known to tumble out of my mouth. The word unfortunately figured large in my undergrad degrees, and I had to say it aloud far too many times.
Electricity.
Different syllables are stressed the way it was pronounced in Pakistan (born and raised) and the US (25+ years). I tried to change to the American way, then got so self conscious, I can’t say it either way. For more than twenty years now!
I haven’t tried to change my pronunciations of any other words (I still say pah-st, fah-st and to-mah-to) but my brother in law used to get after me for electricity.
February. I know that Fe-b(y)oo-ary is acceptable, but it doesn’t seem to be the primary and I think I’d kill myself if I had to pronounce it correctly.
NotherYinzer, another one here from the Burgh, who says Saturday the same way. My partner mocks me with “Sarrrrday.” I think it’s a Burgh thing, from being from donton. 
For some reason “orchestra” messes me up, like I keep wanting to say or-chest-ra, with the hard ch.
Raleigh. I always want to say “Răll-eh”, not “Rälly”. I can never remember the proper pronunciation.
Not that I have to say aloud the capital of North Carolina much, but every so often, when I need to refer to it, I cringe, and just slur it out real fast, mixing all the vowel sounds like Chewbacca, hoping no one notices.
Ahh, I forgot about “peculiar”! Such a peculiar word. I have trouble with it as well; I often find myself slowing-way-down when I get to that one. 
Now I have an image of Chewbacca howling out Raleigh, or trying, as if he’s howling at the moon. [shakes fist]
He’s howling at the hellscape that is Endor’s moon. It’s the sound of a blender gargling a few dozen tennis balls.
So majestic.
Antananarivo. There’s one to many an’s.
Pfttt. That’s because they don’t know to pronounce their own name. It SHOULD be an-TANA-nar-EE-vo. See, much better. 
Vulnerable, for some reason I must put a “g” in it.
There used to be a local news anchor here, who had trouble pronouncing his own name. He’d say his first name, then pause and over-pronounce each syllable in his last name. Very strange.
I don’t even attempt ‘rural’ any more.
mmm
Planetarium