The UE Megaboom is on the pricier side of the dollar scale, but its biggest claim to fame is VOLUME! This thing can get even uncomfortably loud. For most people, there will seldom be a time where you want to turn it up to 11. The Megaboom also sports a IPX7 rating, meaning it can be dunked in any body of water up to 1 meter for thirty minutes. The battery is rated to last 20 hours—which given its size—is respectable.
If you happen to have any of Ultimate Ears' other speakers in their line (like the the Boom or Boom 2), you are able to pair up to 50 of them simultaneously to a single phone.
Get it on Amazon for $240.