Edward Newgate's Bisento

Edward Newgate's main choice of weapon was shown to be a Bisento, a huge and heavy Japanese polearm.

It's a massive weapon, fitting the size of his owner, with a striped pole (with the stripes being all plain brown in the anime, and recently revealed red and yellow in the manga) ending in a spherical edge, and a curved, large blade attached to the pole via a golden part, decorated by what looks like a sea snake, with a thin part of it protruding on the blade itself.

After his owner's death, it became a marking for Newgate's burial site, with his coat, a bouquet of flower, and the crew's flag hanging from it.

Abilities
With Whitebeard's immense skills and powers, the bisento was strong enough to clash with Shanks' saber, which caused the clouds (and even the heavens) to split. Also, the bisento is extremely durable, as it stopped Akainu's magma attack without melting or any visible damage. The bisento could also be used in conjunction with his Devil Fruit power to maximize the devastation done by his attacks, or even be imbued with Haki to harm Logia users.

Trivia

 * The bisento is one of the three attributes (the other two being the Gura Gura no Mi and the status as a Yonkou) that made Whitebeard resemble the Greek God of the sea, Poseidon, who wields a trident. As they are both polearms, the Bisento is analogous to the trident.