Words that just sound funny.

Proboscis.

Proboscis. Proboscis. Prooobooooskisss.

Yep, Proboscis.

Was

Turd. Even people who curse a lot blanche at the word turd because it just sounds dirty.

fasciculation

I can’t even figure out how to pronounce that, but I’m sure it sounds weird.

Of course, we’ve brought in a whole lot of foreign words. (I claimed all of French, above).
One might say, all of Russian too. Ever listen to a tape recording of English speech played backward? (You could do that with old 2-track tape recorders.) That what Russian sounds like to me.

synagogue (mentioned above) for example, is Greek.
halleluyah (or hallelujah) for example, is Hebrew (possibly Greek-ized, I’m not sure).