Individual IOs:
Blessing of the Zephyr, Mag 4 - Universal Travel
Karma, Mag 4 - Defense
Steadfast Protection, Mag 4 - Resistance
Set bonuses:
Kinetic Crash (4pc), Mag 3 - Knockback
Overwhelming Force (6pc), Mag 4 - Universal Damage
Fury of the Gladiator (3pc), Mag 3 - PBAoE (PvP)
Gladiator's Armor (3pc), Mag 3 - Resistance (PvP)
Gladiator's Javelin (5pc). Mag 3 - Ranged Damage (PvP)
Overwhelming Force is the only one that is technically 'Unique'. Expensive both in influence cost and slots, but it's a good set just for it's stats, set bonuses, and the knockback to knockdown conversion. Easy to get if you don't mind grinding Summer Blockbuster (SBB) 6 times and using a few converters.
Every thing else can be stacked up to the "rule of 5", though you shouldn't really need more than 7-8 mag.