Charizard is a playable character in the Brawl mod Project M. It has been separated from the Pokémon Trainer and so fights alone. Charizard was heavily buffed from Brawl, gaining several new moves that are more useful than their predecessors, as well as getting speed and power buffs to its other moves.
In Project M, Charizard leaves behind the slow, tanky attacks, stamina system, and negligible defensive type effectiveness it was known for in Brawl. Instead, it fights alone with a quicker moveset optimized for taking its battles to the air.
Much of Charizard's moveset was given tweaks to encourage a quick offense. Its neutral attack and all of its tilts can combo into themselves, while its down-tilt has a powerful sweetspot that can semi-spike; its smash attacks and aerials all have increased speed or KO capabilities, and its down-smash can now serve as an edgeguarding tool. In particular, Charizard's new forward-aerial trades its predecessor's range for speed, damage, and strong diagonal knockback, making it a potent KO option especially when SHFFL'd. Charizard's new glide attack also has substantial KO potential and its hits link together even at high percentages.
While Flamethrower remains untouched and largely situational, Rock Smash was replaced with a new side-special, Heat Wave. It trades some damage potential for speed, range, and knockback, giving Charizard a faster KO move when used up close while providing an acceptable spacing option otherwise. Charizard's reworked up-special now functions as a single, strong hit, and the purely horizontal knockback it deals at the start can help Charizard break out of combos.
The biggest change to Charizard's moveset, however, is its new down-special, Fly. When used on the ground, Charizard will lift off in a high jump, achieving heights otherwise out of reach while providing greater speed than its jumps and up-special. Fly can be angled, used immediately or charged for nearly a second, and Charizard can cancel it into any aerial or special move while preserving all of the move's momentum. This gives Charizard incredible chasing options after launching a foe; it can rack up further damage (using neutral or up aerials), it can quickly meteor smash opponents recovering high (down aerial off of an angled Fly), it can semi-spike (back-aerial or close side-special), or it can go for a KO off the top (forward-air, glide attack, or late up-special). Many of Charizard's ground moves are designed to pop foes into the air where they can be chased with Fly, especially its new up-throw, which deals strong damage and vertical knockback that can leave damaged foes close to the upper blast line.
Charizard's defensive weaknesses are still present. While it has impressive dashing speed and range on its ground attacks, opponents with disjointed hitboxes and projectiles can easily wall Charizard thanks to its large hurtbox. Charizard also has very limited options for dealing with attackers below it, making Fly a double-edged sword if an opponent can reach the stage before Charizard can. Charizard remains weak in recovering horizontally, as its glide will not reset if Charizard is hit, forcing the use of its glide attack to power through edgeguarding.
As a result, much like in its home series, Charizard can't give its opponents the time or position to strike back, as its weaknesses are difficult to cover. However, when played to its strengths of speed and aggressive attacks, Charizard can easily dominate its opponents without letting them take advantage of its shortcomings.
Changes from Brawl to PM
Charizard has been noticeably buffed from Brawl to PM, while also receiving many new moves and changes. Like Squirtle and Ivysaur, Charizard is now a separate character from the Pokémon Trainer. The main benefit this provides is that Charizard no longer suffers from the Stamina system and it no longers suffers from the risk of changing Pokémon and being heavily punished for it. As for its individual buffs, Charizard is much faster both in terms of its movement and in the speed of its attacks and a fair amount of its attacks have increased KO power or combo potential.
Charizard has also seen a few nerfs. As it is no longer tied to the Pokémon Trainer, it can no longer swap out with Squirtle and Ivysaur to gain access to a smaller hurtbox, greater mobility and zoning and to generally cover up its bad matchups. As for direct nerfs, some of Charizard's moves have seen a decrease to their speed, range or power.
Overall, Charizard is a considerably more effective character and as of the latest tier list, it outclasses its fellow party members.
Up to date as of version 3.6.
In competitive play
Charizard now has more significant, independent palette swaps. It also gains a costume based off the armored Charizard seen in the beginning of Lucario and the Mystery of Mew. The same costume received a black recolor based on Aggron in Project M 3.6 Beta.
Some of Charizard's alternate costumes are based on different Pokémon:
Coincidentally, most of these Pokémon in the main games have dragon-like properties (Golbat being the exception), like Charizard, by either being capable of learning a variety of Dragon-type moves, or being commonly owned by notable Dragon-type specialized trainers.
Z-Secret Costume: Mega-Charizard X
R-Secret Costume: Mega-Charizard Y