Joseph Bottum at First Things talks about agenbites (his coinage)
I've come up with a few.
How about parallel. You don't even need to pronounce it to know. Just look at it. There are two sets of mirrored letters, one set divided by a consonant, the other by a vowel. Could there be a more parallelistic word than parallel?
Perhaps that's an even better one: parallelistic.
I think the agenbite-worthiness of gargantuan is rather self-evident.
And then there is incapacitate. You notice how all or most words beginning with in seem to suggest a convolutedness? Invert, instigate, incest. That's no wonder, considering how one has to go through the trouble of touching the roof of the mouth with the tongue in order to pronounce it. Not a smooth way of starting a word.
Perhaps geometrical terms provide some interesting agenbites: conical, trapazoid, cylindrical, angle, obtuse...
Then there is God. Is there a more self-contained word? It begins and ends with a consonant; no trailing-off, airy vowels to end the word. No effeminate beginning vowels. And both bookend the most self-contained vowel, the circle of the 'o'.
When you think about it, it is actually quite spooky.