Agreed with Jebus and Renosaur. Corki and MF are fantastic recommendations. Caitlyn and Graves aren't bad recommendations, either; they're generally good recommendations for anyone looking to learn ADC due to their simplicity, forgivingness, and all-around strength in lane. (MF and Corki are PARTICULARLY forgiving.) While someone who likes Malphite might like to play Leona eventually, I never advise Leona to be someone's first support if they don't already play bot lane, because the trick to Leona isn't hitting your Zenith Blade (easy), it's knowing how and when to go in, it's understanding zoning and the pace/flow of the lane, which is something you pick up by experience playing in the lane as general. Once you have that experience then it gives you a solid foundation for playing kill lanes.
Support Zyra is also a kill lane with immense poke and range elements (meaning it's a more forgiving kill lane than Leona because you snare them from huge range rather than jumping directly into them with no escapes, and because you can play defensively), and the other thing is you could also learn her as an AP carry, since you play Lux, so I second that recommendation. I don't think you would enjoy Soraka or Nunu but that's because I think they're boring as hell; I think you'd like more aggressive, pokey supports, and while Sona might be faceroll, playing her aggressively, zoning with her, and poking is really enjoyable for me. I also think you would like Lulu a lot, although she has a higher skill floor than the supports Jebus listed, for similar reasons. She's a very fun champion with a lot of poke and range. I think if you like Maokai or Cho'Gath then you might like Lulu quite a lot. (I do main Sona and Lulu and am actually picking up Zyra, so I might be biased, but I play them for those reasons, so I think I'm qualified to offer this opinion?) Soraka is very useful to know for ranked, but anyone can play her, so don't worry too much about it. You can play Lux as a support although opinions on its effectiveness vary and you might get people mad at you for playing it in ranked, whereas almost nobody is going to object to support Zyra, since it's very established. It's also a nice ambiguous pick, since they don't know if you're going to play mid Zyra or support Zyra if you pick it before the other role is picked.
I think someone who likes all-in bruisers like you do would definitely come to love Leona, but learn some of those supports before trying her, unless you want a string of very discouraging, unfun games because you don't know how bot lane works. ;p
PS: I think MF Soraka is not a great lane -- sorry, Renosaur! MF works best with champions who can support her aggression and bully the lane hard. Soraka is not a good bully and MF wins trades through right-clicking with w on. The ult mana cost was buffed awhile ago, if you don't spam Make it Rain and use Double Up to cs every wave, preserving mana for trades, then I wouldn't worry about it. Soraka Corki is a fantastic lane though. Corki does a lot of magic damage so Starcall's MR shred is very welcome, and because when he's bursting them down constantly he's VERY mana-intensive, unlike Miss Fortune, so Soraka gives him an infinite damage engine. Corki has his own escape too, so he doesn't need Soraka to help him there.
I think the best support for Miss Fortune is Sona because of their ult combination and the fact that Sona plays very aggressively and pokes hard with massive early burst. They win lane super hard together. I think Nami will be a fantastic support for Miss Fortune as well; I think MF is one of the best carries for Nami because of their ult combination, Nami's CC setting up easy kills, and Nami's incredible E steroid working so well with MF's. I've been playing a lot of MF/Lulu lately as well, playing it like an MF Sona lane with lots of peel for MF, who needs it because of her lack of escape and mobility in teamfights (it's a hard to gank lane as well, hell, don't even put a point in Make it Rain when Lulu has Glitterlance). MF works well in kill lanes as well. I think a passive support is very wasted with Miss Fortune and Soraka doesn't really have much to offer her, since she is not that mana hungry and MF actually has quite good base stats, meaning Soraka's armour buff isn't even that fantastic when you compare it to what the supports I listed offer. I also think that while MF is a great all-around lane-bully AD, comps that make the best use of her have a lot of AoE CC (her ult actually does a lot of damage after lane, but not if you have no AoE CC), which is why champs like Sona and Nami are great with her 'cause they do the wombos.
Source: The AD I play with can't play anything but Miss Fortune and Corki, maybe Caitlyn on a good day, so probably like 2/3 of the normal games I've ever played are in Miss Fortune lanes.