Mega Man (ロックマン, Rockman) is a newcomer in Super Smash Bros. 4. He was announced at Nintendo's E3 Direct Conference presentation for the game. It has been said that he does not widely use hand-to-hand combat, but relies on his large arsenal of weaponry. This is somewhat analogous to, but to a further extent than, Snake in Super Smash Bros. Brawl.
In a demonstration battle between Mega Man and Mario, Mega Man can be seen using what appears to be a taunt, where he warps out and immediately back on the stage, similar to his warping animation in the classic Mega Man games. 
Up special move: Rush Coil. Mega Man briefly summons his trusted dog, Rush, who acts similar to Sonic's Spring Jump. It seems that a second bounce will make Mega Man jump even higher than the first bounce. If the move is performed while Mega Man is grounded, his opponents will also be able to bounce on Rush.
His default coloration, with blue and light blue armor.
His armor is red and white. Likely based on Mega Man's color scheme when using Rush, first appearing in Mega Man 3, or the Rush Adaptors first appearing in Mega Man 6.
His armor is dark green and white. Similar colors are used by several weapons in the series, but it closest resembles that of the Leaf Shield from Mega Man 2.
His armor is bronze and pale yellow. This is nearly identical to the palette swaps of the Metal Blade from Mega Man 2 and the Ring Boomerang from Mega Man 4, and similar colors are used for the Thunder Beam from Mega Man and the Thunder Wool from Mega Man 10.
Mega Man is shown to have a slightly different KO explosion, the only character shown so far in Smash 4 (and, by extension, the entire series) to have this feature. Instead of just a single blast of the color of the player port, he also splits into blue orbs in a similar fashion to when he loses all of his health or lands on spikes/lava in Mega Man and Mega Man 2.
The promotional poster artwork of Mega Man used on the Smash 4 website mirrors the style of several Mega Man game covers and posters, such as the Japanese Mega Man 7 boxart, in which Mega Man stands in front of a group of allies and/or Robot Masters with the main antagonist looking over from the top.
Mega Man's artwork used on the website was illustrated by Ryuji Higurashi of Capcom.