I love controllers and alts. After trying out many types I narrowed it down to 7 primaries and 7 secondaries I liked. Then I looked at how they play to pair them up. My consideration was active vs passive (pre-buffing in combat or toggles is passive), pbaoe/cone/range, and End usage. I came up with these 7 combinations that let you try all 14 sets with no duplicates. Note that I made no consideration of power level, end game play, IO sets, etc.
Primary
Secondary
Darkness
Thermal
Earth
Darkness
Electric
Kinetics
Fire
Radiation
Ice
Time
Mind
Empathy
Plant
Nature
Darkness/Thermal – Darkness uses a cone starting at 8 usable every fight. And with a ST hold and a ST confuse every 8 seconds it is very active. So I paired it with Thermal that is largely a pre-buffing set with a ranged heal, so you can spend your time in combat using Darkness and be back with your cone.
Earth/Darkness – Earth and Darkness are both largely ranged aoe sets. Earth lacks strong control early on, so it benefits from Howling Twilight. And the -Def in earth makes it easier to hit with Twilight Grasp for your heals.
Electric/Kinetics – Electric has ranged but you want to be in the middle of your foes with Conductive Aura. That works well with standing next to your target for Transfusion and in the midst of your allies for Siphon Power.
Fire/Radiation – Fire is a weak control set at low levels so you rely upon radiation for mitigation with its toggles. And at lower levels your powers are all ranged except hot feet if you want to use it. So you have a lot of flexibility of movement in combat.
Ice/Time – Toggle on Arctic Air and Time's Juncture, stand in the middle of your foes and they are slowed and confused.
Mind/Empathy – Mind has a ST sleep, hold, and confuse making it very active. Empathy mostly buffs with auras plus healing. So you can spend your time in combat using your mind powers.
Plant/Nature – A standard combination but the cone use of Seeds of Confusion and Regrowth makes these play well together.