Neccessary
Aquisition
Guaruntee
Absorbtion
Recieve
bureaucratic
I even have a hard time getting close enough for spell checking to recognize it enough to make a suggestion
recipe
while my recipes tend to come out right, the word never does
thorough and throughout
not spelling-challenged per se, but I tend to lose my place syllable-wise
Embarrass.
One “r,” every single time, unless I look it up. grrrrrr…
Accomodate.
Apparently. I never can remember if it’s the p or the r that gets doubled, which is strange because I use the word a lot.
weird
“Wrong,” of course.
d&r
Restaurant. I recently got tired of not remembering how, so I finally broke it up into rest, au, and rant. So I get it right about half the time, now.
I always want to add an extra “s” to occasion. I also sometime transpose the “s” and the “c” in “license,” but it immediately looks wrong.
I once lost a spelling bee with this one in primary school, so it’s been burnt into my memory banks ever since.
I always have trouble with the two forms discrete/discreet.
Spell check is the best invention that ever was created!
I can look up a word, close the dictionary, and immediately forget how it was spelled. It is horrible. Oddly enough, I am now very good at noticing when a word is misspelled…it is correcting it that is the problem.
Plus, I always hated dictionaries…how the hell was I supposed to look up the spelling if I didn’t know how to spell it?
Thank you for spell check! Thank you, thank you, thank you!
Anything ending with tly.
or with gry. That makes me … well, you know. 
Since I’ve just used this in a post…“separate”, or how I invariably end up spelling it “seperate”, phonetic vs actual spelling always used to throw me for a loop when I was a kid and some of it has carried over.
As an aside, I’ve had two weird ‘blind spots’ when I was at school. I was what they called then ‘top streamed’ for Maths and English (three tiers of class for each subject of which I was the highest in each) BUT I couldn’t spell very well and I couldn’t do my times tables very well. At the start of every Maths class our teacher used to make us do a five minute randomised 10 x 10 times table square (up to the 20 times table) and I never finished it. Even to this day if I’m asked or I need to know what, for example, 9 x 6 is I break it down to work it out, my thought process is “2 x 9 = 18, 18 x 3 = 54”.
…thankfully my spelling has got better, mostly!
Belief, believer, beliefs, etc ( and yes I did just misspell and have to correct one of them again ). I always seem to reflexively spell them with an “ei” and not an “ie”.
Exercise. I cannot get this word right in fewer than five tries. I can’t figure out if there is a “c” after the “x”, or whether it’s spelled with a “z” or an “s”. I had to try every iteration I could think of just to make this post.
Floccinaucinihilipilification? Antidisestablishmentarianism? No problem. But “exercise” gives me fits.
Neighborhood and
Rennaisance.
see?
Accommodation is my bête noire.
This is what I came here to say – I’ve yet to figure out the particular mental block that goes with this one 
I just recently learned there’s “a rat” in separate.
Vaccuum is one of mine (or is that vacuum?) And I use it often in my job (the word, not the appliance.) There are a couple more than aren’t coming to mind right now. I think “weird” and “friend” are up there. I’ll check back when I come across them while typing today.