#6 Bam Margera Presents: Bamination
Bamimation is an MTV dropout courtesy of Bam Margera and the musical group CKY, all of whom appear in this pilot episode which involves shrink-rays, scalping and (naturally) Bam's adolescent sense of humor. As interesting as this one could have been given the Looney Tunes style of slapstick, the quality just doesn't really compare to the others listed here.
#5 Plastic Man
Now here's a pilot that lends itself to some possibilities. Take Plastic Man's "elastic" charisma and give it John Kricfalusi's (Ren & Stimpy) visual style style and you have a toon that's built for laughs and larger than life action. They even had the perfect leading voice actor in Tom Kenny of Spongebob fan.
#4 The Amazing Screw-on Head
Thanks to Andrew for pointing this one out to me. Seems as though the tv debut of Mike Mignola's quirky detective, The Amazing Screw-on Head, was actually intended to be a Syfy Channel exclusive back in 2006. The network put the pilot to an online vote (which it apparently lost) which is unfortunate given the its unique style of action and comedy, not to mention it's steampunk aesthetic. Fortunately the pilot was released on DVD, though a series still would have been pretty sweet.
#3 Buffy the Vampire Slayer: Animated Series
This animated pilot has some real "bite," especially since it was backed by creator Joss Whedon and comic scribe Jeph Loeb. Stuck in development hell thanks to Fox Kids ultimate demise, this pilot was produced in 2004 to try and sell the concept to networks. Unfortunately, the concept was deemed to adult-oriented for kids' programming yet not adult-oriented enough for prime time. Shame.
#2 Rat Bastard
Based on a late 90s comic created by Cliff Galbraith, this pilot features Detective Roscoe Rat in a Blade Runner-esque world where mutants and monsters are commonplace thanks to DNA experimentation gone wild. Part hard-boiled noir, part sci-fi Rat Bastard would easily become Adult Swim's crown jewel if given the greenlight.
#1 Korgoth the Barbarian
Without a doubt Korgoth is the most bittersweet pilot on this list. A classic spoof of Conan the Barbarian, this short was directed by none other than Genndy Tartakovsky (Samurai Jack, Star Wars: Clone Wars) with Diedrich Bader, Corey Burton, Susan Spano and Tom Kenny filling out the voice talent. This one has it all... it's funny, action-packed, loaded with ludicrous amounts of gore, and there's even a (semi)intelligent plot.