I pronounce Buizel as "buy-sell", more or less (can't think of anything in English that sounds like how I pronounce the ui sound). I'm pronouncing it as though it were Dutch (which is my native language). I would transcribe it in IPA but I can't be bothered to go find the right symbols so nyah. P:
For the Nidoran lines, I always say 'nehh-do' instead of 'nee-do'. I pronounce Phanpy as 'fan-fee'. Until recently, I pronounced Regigigas as 'ruh-jehh-jehh-gaas'. Mm, I probably pronounce a lot of others wrong, but those are really the only ones I could think of right now.
I mainly stick with the Japanese names nowadays, and in Japanese, things are pronounced exactly as they're spelled. Though, I do like to think that Rayquaza, since its romanization was apparently the same in both versions, was meant to be pronounced in an English-speaking context as "Reh-kah-zah" instead of the "Rey-kway-zah" that the official media's got (Rayquaza looks to have had some influence from the Aztec Quetzalcoatl, so it wouldn't be that unusual to pronounce a "qu" as a "k"). Also, I don't know where Nintendo of America got that hard "K" sound for Arceus even after they pronounced it correctly in Battle Revolution. Though, it's all kind of a moot point since I don't talk about Pokemon much in real life (or am much of an active initiator of social conversation at all, really).
As many others, "Arceus" comes out "AR-see-uss." I actually didn't realize it was wrong until now, haha... XD Um, other than that all I can think of is Bonsly, which I say as "bons-lee," like how they say it in the one movie (forgot which). It was the first time I heard its name aloud, and I thought it was accurate until I looked it up. XD I don't say it "bon-sly" (like bonsai, almost) because I think it sounds silly, and the voice actor for Bonsly in the movie made it sound sooo cuuute. <333
I pronounce Arceus as ARC-eh-us or ARC-ee-us. I use these two back & forth. I pronounce it like that because a "c" is always pronounced like the English "k" in Latin. (The Latin language rarely uses "k." In fact, the only example I can think of is "Karthago," meaning Carthage.)
For a while, I called Kangaskhan "KANG-za-kan" because I picked it up from my brother. I stopped calling it that when I realized that wasn't how it's supposed to be pronounced. On the topic of mispronunciation & my brother, he once pronounced "yacht" as YATCH-et.
Gible for me is GUY-bul because Gib-bul just sounds ridiculous.
Arceus for me = ARE-see-us
Giratina for me = Dji-ra-tee-nah (which sounds like an eastern delicacy )
Milotic with either the emphasis on MI or LO, I interchange those constantly.
I usually don't care for the "official ways" to pronounce their names, as I pronounce them however I think they are at first. After that, even if I'm completely wrong, I'll keep to my ways. Here's my list:
Sceptile: (skep-tile) -I don't like the official (cep-tile) form, it doesn't sound as cool.
Rattata: (rad-uh-tuh) -One of the biggest ones that I refuse to give up.
And many more that I have forgotten right now, or did eventually "correct" and have forgotten how I originally said it (most from the Hoenn saga).