Magical Focus
In Fifth Edition, Major Magical Focus and Minor Magical Focus are (Major and Minor) Hermetic Virtues. A character may only have one Magical Focus.
A bone of contention is the Minor Magical Focus in Certamen granted as a free Virtue to House Tremere. It has been criticized as being too broad for a Minor Focus, however Timothy Ferguson has defended it on the Atlas forum,
Certamen's not "too broad". It does cover all forms and techniques, but only on occassions of magical dueling between consenting parties. I mean, its contextually so narrow that it is almost worthless. It is worthwhile if:
the other guy doesn't have it.
the Tribunal won't just over-rule the whole thing
the loser isn't willing to go to Wizrd's War
both sides can't just hire someone with it.
So, it's a very, very narrow focus...and the opportunity cost is huge. Sure, you are a good duelist in very limited circumstances, for which you gave up what? Healing? Flames? Commanding mortal armies?
The House Virtue is also often criticized for the opportunity cost Timothy mentions, and it is a common House Rule to allow a second Focus or another Virtue in its stead.
Another controversial focus is the Minor Magical Focus in Swords, granted by the Confraternity of Roland in Mystery Cults. Arguably, the increased power is acceptable as it is a Mystery, rather than a usual Magical Focus.