What is the most FUN pair of speakers you've ever had and why?

For me it was the Polk Audio LSi 15

Not the most refined, and far from the most expensive I owned ( those would be a couple of Verity Audio speakers I owned in the past}.

The LSi 15 sounded...RAW, alive and very dynamic. No exceptional bass, or high frequencies, although those ring radiator tweeters were pretty good.

Can still be had for audiophile peanut$, I remember reading a review that mentioned they compared to 5k speakers, and they did. I had a big McCormack 225 amp and Cary tube preamp at the time. But the Polks sounded great even with the diminutive Arcam A85 integrated. That last inexpensive combination could still be an extraordinary bargain today.

A lot of fun with no bragging rights, but amazing performers still.

Man, this was long time ago, but here goes. I had just gotten ripped off by the local music store owner for a pair of John Zeer speakers. I lost $380 of really hard to earn dollars back in 1975. That got me starting to look at the other end of the spectrum. If JZ was crap, then what was the best (according to a high school junior)? From what I could gather in my cowtown in Wyoming, it was the K horns. Great, how much? Too much for me. Then I discovered Speaker lab in Seattle. They had a kit in which you could copy the Khorn design called the Speaker lab K. Ok, so I built the pair in my senior year in woodshop. Everybody was shaking their heads. Why was the driver inside the cabinet like that? 
 When finished, I was to never hear bass like that ever again. The midrange and tweeter horns were ok, mind you but the bass was pant leg rattling. What more fun could any high school kid have than to own a pair of these?

They were Speakerlab K's for me too!  Sometime in the early 1990's one of my coworkers took a job in Alaska and did not want to transport his pair all that way and asked if I was willing to give them a home.  I do not have them anymore, but only because the octagonal configuration of my current residence is simply not corner horn friendly.  I very much miss that 'massive' sound though! 

Tekton Pendragons - the most fun I’ve ever had in a speaker, they just get cleaner and overwhelmingly powerful the louder you play them. Every time I really push them it just makes me giggle, I can’t believe they can produce concert level sound and stay absolutely clean and retain such intricate definition. Definitely make ya smile!

@ asat:  I hear you, buddy.  Totally understand.