I'm going to chime in on the Mage argument. The system works OK, although the "swap merits for Gnosis" rule means that all characters start with Gnosis 3 and Order Status 1 or else shoot themselves in the foot (free High Speech).
Aside from that, the arcana are actually somewhat balanced, but they all have their "good" and "bad" dots. For example, the Life arcanum is fantastic at 4 and 5 dots, but leads to huge redundancy if you only have it at 2, since everyone now needs it. Prime is similar; having a single, highly skilled character (Supernal Dispellation, Create Hallow) is very, very useful, but the lower dots are slightly meh. Fate and Time, on the other hand, are very valuable at the low levels; Time 2 and Time 3 are very nifty, but Time 4-5 doesn't really add that much except better Postcognition and dice pools.
Also, I'm actually discussing Mage: The Awakening, as I think Rev might be.
One completely broken trick: Do something in a Hallow while you have Time 3. If you don't like the result, cast a reflexive Glimpsing the Future on it. Should you fail witht he spell, cast a reflexive Glimpsing the Future on that. This allows you to reroll arbitrarily many times until you get a result you like. Since the nWoD d10 system rerolls 10s, this allows you to accumulate any number of successes in a single round, starting with any dice pool; even a chance die (0 dice). The Hallow negates the cost of the Glimpses.
Also, Time 3 is within the reach of a starting character. As is one dot in the Hallow merit.
Dammit, I just discovered another Pun-Pun.
What I like in a system? Good character creation rules, where you have a few different options that will actually affect what your character does, rather than just how good he is at [Role]. Oddly, I still like 4e, as the two "build options" are actually different quasi-roles - an Orb Wizard is a full-blown Controller, while a Wand blaster wizard is half-striker.