Nice thread.
My top 5 are:
Crystal Maiden - Her passive is incredible, her ultimate is deadlier than your opponents ever seem to expect, her Q is one of the best laning harassment skills in the game and her W is all you want from a single target stun: interruption, good duration and fair damage. She is my #1.
Wisp - Great chase and escape; a survivable ranged strength support with global presence for you and a friend. Spirits are a fair nuke, overcharge is tops for pushing down towers. This hero has few weaknesses. #2 no problem.
Juggernaught - Q is a Free BKB and he has a great animation. Pick up treads rather than phase boots and you'll have no mana problems. His in built critical has very high odds, his ultimate eventually lasts a long time while making you immune to rightclicks as well as spells (oh, and it does a tonne of damage)... Just a solid beginner's carry, with enough nuance to be relevant at the highest levels of play. Plus a great voice set. He's an honourable #3.
Lina - Lina was the hero I played first after installing Dota2 (I was long ago a fan of the anime that is the basis of her WC3 DotA incarnation). Dragon Slave and Light Strike Array are both excellent laning skills, though the latter can be tricky to land without surprise or a prior snare. Her passive is one of the best in the game and keeps getting buffed! Her ultimate is the highest single target burst damage skill in the game, and can spell the end of other support heroes even if they're up at around 80% of their life points. Lina should be in everyone's top 5. She's my #4.
Bane Elemental - Possibly the scariest support hero in the game, with even more ganking and solo-killing potential than Lina on account of the fact that Fiend's Grip goes through BKB and his disables are targetted rather than skillshot. Laning against Bane can be demoralizing. His animation is great, his base damage at level one can fast bring you low enough for a play on your life to be made and oh yeah- he looks like the ghost of a fucking xenomorph. He's #5.