The list of Merits and Flaws in the Revised Mage: the Ascension was expansive and top-notch, so I can only add to it marginally. Consider this modest page a suppliment to that work. While I hope you find my work useful, be sure to check with your Storyteller before taking any of these Merits or Flaws and unleashing their effects in-game, okay?

Distinct Willworking (2-pt. Supernatural Merit)
The mage begins the game with two dots in each Resonance trait, instead of one. This Merit is common among those with high Avatar and Destiny ratings.

Distractions (3-pt. Mental Flaw)
Be it from physical pain, a continual buzzing, or mental fugue, the Distraction Flaw makes it difficult for the Willworker to concentrate on mundane tasks or perform them effectively, as her Paradox works on her mind in unpleasant ways; the more Paradox a mage has earned, the more severe the distractions become. While she can channel Sphere effects as easily as ever, Distractions can hinder a mage enormously when she attempts simple tasks like filling out tax forms, remembering facts regarding a subject of study, or even operating a computer. This might encourage a Willworker to rely on magical aptitude to overcome her disability, which may garner her more Paradox and exacerbate the problem. Each point of Paradox in the mage's system increases all Mental Attribute difficulties by 1, though this penalty may be overcome for a turn if the character spends a point of Willpower.

Divergent Paradigm (1-pt. Supernatural Merit)
Every mage's paradigm is unique and individualized, though some paradigms are more individual than most. This Merit allows a player to "switch out" his character's Specialty Sphere (as per his Tradition) for another, befitting the character's paradigm and means of working magic. For example, a Hermetic metallurgist and alchemist may have Matter has his primary Sphere, Life might reflect an Ecstatic yogi's mastery over his body and metabolism, while a Syndicate efficiency expert might find Time comes to her more easily than Entropy.
The chosen Sphere is treated like a Specialty Sphere in all ways; the character's first, "free" dot is put into the chosen Sphere, and exp costs for that Sphere are calculated appropriately. (The "old" Specialty Sphere, on the other hand, is treated like any other Sphere for that character, and the player may or may not choose to invest dots in it.)
Divergent Paradigm is meant to provide story potential, a way to define a unique character -- not a way to abuse the system. Storytellers should be wary of those who choose Spheres without rhyme or reason. And some traditions may be too married to their Tradition Spheres to allow much deviation; for example, it would be a very unusual Dreamspeaker indeed that didn't develop Spirit more easily other Spheres, and an Akashic Brother or Man in Black without any Mind probably has a player to match.
Hollow Ones and other Orphans may not take this Merit, for obvious reasons.

Focused Mind (3-pt. Mental Merit)
The character is confident and sure of her abilities, and knows when to exert herself and when to hold back her reserves. Up to three times a day, the player may choose to spend one of her character's Willpower points after the roll is made, rather than having to call the expenditure beforehand. This allows more efficient use of Willpower, allowing players to cancel unexpected botches and not waste Willpower points on rolls where the extra success isn't needed. A character can still only spend one Willpower per turn this way.
A player may not choose to spend Willpower based on the results of others' rolls, only that of his character. For example, he can choose to spend a Willpower after his character attains only a marginal success on an attack roll, but he can't spend a Willpower to cancel an opponent's single Dodge success.
A character must have at a Wits of 3 or higher to possess this Merit.

Linked Spheres (2-pt. Supernatural Flaw)
The character's understanding of two Spheres are so closely related that, to him, they are inseperable and in fact may as well be one Sphere. While most mages understand how Spheres are closely related, a Willworker with this Flaw is unable to see the distinction between the two Spheres. Invariably, one of the Spheres is the mage's Specialty Sphere, as the Linked Spheres reflect an essential limitation in the mage's paradigm. Advancement in one Sphere is impossible without a commensurate increase in the other; when an increase in either Sphere is desired, the player must spend enough experience points to increase both Spheres simultaneously or neither will improve. However, to make up for this somewhat, both Spheres have their experience multipliers decreased to x6. (However, the experience point costs to raise both Spheres still have to be paid!)
Dreamspeakers are particularly subject to the Linked Spheres Flaw, as most perceive everything as shadows of the spirit worlds. Several Euthanatoi understand the chance and fate manipulation provided by Entropy to be links to the fundamental energies of the Tapestry, tying it strongly to Prime in their paradigms. However, Linked Spheres is most often exhibited by technomages who cling strongly to established scientific theories. Several Virtual Adepts and Void Engineers see no difference between Time and space (Correspondence), while some Sons of Ether and Iterators recognize Matter as just another form of energy (and thus governed by Forces). And Progenitor psychopharmacologists often see Life's control over the chemical and physiological processes of the brain as control of the Mind.

Paradox Sickness (3-pt. Physical Flaw)
A character with this Flaw can't assimilate his Paradox very well, and has something of a physical allergy to it. The unstable energies of Paradox may cause muscle cramps, nausea, pain, or fatigue and weakness; in any case, it impairs the mage's ability to function at low levels, and may cripple him outright if Paradox builds too high. For each point of Paradox in his system, all the Willworker's rolls involving Physical Attributes have their difficulties increased by 1; a Willpower may be spent to cancel these penalties for a turn. Such characters would do well to mind themselves and stick to coincidental magic.

Refined Avatar (2-pt. Supernatural Merit)
The character efficiently processes Quintessence, and is able to draw every bit of utility from that fundamental energy. For every three points of Quintessence the character absorbs (at a node, from Tass, or from another character), he gains one extra point of Quintessence. This extra bit of energy is only applicable to the mage himself, and isn't transferable to other characters or items in any way. The character must have an Avatar of 3 or greater to possess this Merit.

Weirdness (2-pt. Social Flaw)
The mage wears her Paradox openly for all to see, making others uncomfortable. Paradox can manifest in the form of eyes that glow, unusual voice, minor physical abnormalities, nervous tics, and even rashes. The intensity of the problem is waxes and wanes with the amount of Paradox the mage has; glowing eyes will glow ever brighter the more Paradox is accumulated, while a Progenitor whose Weirdness manifests as rashes might only display reddened skin if only suffering from one or two points of Paradox, with full-blown hives and oozing sores with five points or more. In systems terms, the character's Social roll difficulties increase by 1 for every point of Paradox she has; a Willpower point may cancel this penalty for a single turn.
While this interferes with a mystic's social life, it can also draw undue attention from the Technocracy, hunters, and any number of other folks that seek to make life hard on mages. Technocrats who possess this Flaw, on the other hand, tend to be regulated to roles away from the public and watched closely.