There are a lot of them, actually. The most important ones are ~27% Haste, with another ~50% which is generally out of reach without a large haste buff (Heroism, Frenzy, War Machine).
Each of these steps at 17%, 21%, 30%, 37%, 42%, and 50% (values rounded) are also breakpoints, with even smaller steps interspersed between. Remember, breakpoints aren't always as straightforward as "more GCDs during Battle Cry", but can be associated with Enrage, Frothing Berserker, Rage generation, tier bonuses, and so on - meaning your particular gear may shift, add, or remove them entirely.
With Ceann-ar Charger, Haste, Mastery, and Versatility are all fairly consistent, with Haste ahead, Verse/Mastery nearly identical. Note the significant drop with any loss of Haste (moving left).
With Soul of the Battlelord, Haste and Mastery are fairly well intertwined, with a slight peak at ~+1300 Haste (30-31%), and a notable drop off at -1000 (26%). This profile sitting between two breaks illustrates how quickly Haste can go from an average stat to a very important one, depending on how close you are to those points.
When using Soul of the Battlelord, trading Haste for Mastery is favorable up until that same point (~26% Haste).
Without Convergence of Fates, crit rises dramatically, and provides the best balance of stats overall, though Haste still has notable breakpoints (see left side deprecation), and this balance isn't enough reason to drop CoF altogether.
These examples show why it's good to sim your own stats regularly, rather than just once and assuming those weights will remain consistent; however, there remains a constant in that Haste and Mastery remain universally strong stats and they rarely drop for any length of time. Therefore, the easy rule is to simply prioritize those, and sim close gear changes when necessary.