When I flip through any book of monsters, no matter how highly praised (sorry, Monsternomicon), I'm struck with the realization that I'm not going to use most of this stuff. Sometimes, it simply doesn't appeal to me (WotC's seeming obsession with bat humanoids, for instance), but other times, well, other times, a lot of the monsters just seem lame.
But when I express this opinion about a given monster here, there's invariably someone who pipes up with HOW COOL that monster is, or at least now that their DM put some particular spin on it.
So, in the interest of rehabilitating the also-rans of the monster world, what are some formerly lame monsters that you've seen made cool, and what was done to add that crucial amount of coolness?