Well, the title is pretty self-explanatory. We'll get down to business... There are various reasons I like these words; some because they sound nice, some because they look nice, some because they're really hard to pronounce, and some just because they have a nice meaning.

abhorrent--(adjective)--1. Disgusting; loathsome; repellent. 2. Feeling repugnance or loathing. 3. In opposition. [Root word: abhor]
Why I Like It: It's fun to say, and it's a strong feeling -- to abhor.

ab initio--Latin for "From the beginning". [Abbreviation: ab init.]
Why I Like It: I like Latin words, plus "ab initio" is fun to say.

ABO--A classification of human blood types with regard to their compatibility in transfusion. Bloods are typed as A, B, AB, or O.
Why I Like It: When I first saw it I thought it was an alternate alphabet :)

abode--(noun)--1. A dwelling place or home. 2. The act of abiding.
Why I Like It: I thought it was much cooler than "habitat" or "home".

abracadabra--(noun)--1. A cabalistic word held to possess supernatural powers to ward off disease or disaster. 2. Jargon; mumbo jumbo; gibberish. [Late Latin from Late Greek abrasadabra, a magic word used by a Gnostic sect, probably derived from Abrasax, the name of a Gnostic deity.]
Why I Like It: I couldn't believe it was actually in the dictionary and had a whole history to it.

acajou--(noun)--Mahogany.
Why I Like It: Admit it, it's so much more interesting than mahogany.

ameliorate--(trans. verb)--To make better; improve.
(intrans. verb)--To grow better.
Why I Like It: It sounds really cool.

apotheosize--(trans. verb)--To exhalt to God-like status; to deify.
Why I Like It: Just say it out loud!

appassionata--(noun)--Latin for "something to be desired".
Why I Like It: It's beautiful sounding, it's Latin, and it has a beautiful meaning.

cupidity--(noun)--Eager or excessive desire, especially for wealth; greed; avarice.
Why I Like It: It's so much more colorful than "greed".

garrulous--(adjective)--1. Talking too much. 2. Wordy.
Why I Like It: Yep, that's me :)

serendipity--(noun)--A fortunate, unexpected, and accidental discovery. [Coined by Horace Walpole after the characters in the fairy tale The Three Princes of Serendip, who made such discoveries.]
Why I Like It: Yeah, I went out and saw that movie, and it was just too cheesy (I'm a cheesy person, what can I say?)