I love Zephyr's Airburst because it lets me group up enemies together and finish off with other abilities or weapons.
Mag's Pull is also one of the best and my favorite cc abilities in the game, so it's also subsumed the most.
Also Ember's Fireblast, good cc, armor strip, small damage, status effect, good ability overall.
As for specific examples:
Airburst on Valkyr's 3, I love using Venka Prime and her 4 to tear them all apart when grouped together.
Same on Wisp, replacing her 1 (yes, i hate that ability, fight me xD), and using then her 4 to burn them alive! Most fun i've had with Wisp in a while.
Pull on Mesa's 1 for some fun CC while i gain enegry to use her other abilities.
Warcry on Nova's 3 (always hated this ability), in conjunction with Stropha to quickly power up her 1 (orb) for max damage!
Fireblast on Hilrdyn's 3. I never like it, so i but something visually interesting and fun on her, plus i need one less Augment Mod Slot, namely Blazing Pillage to get the same effect ^^
There are more, but this is pretty much it for now.
Have fun Tenno ^^