I absolutely ADORE off meta supports, allow me to list some of my favorites :D
Full ap cait is a beast, honestly she's pretty cheesey but she does an amazing job at stopping jungler in their tracks and assisting her ADC kite. Also if your opposing support is stupid, stack three traps at level 1 in the same spot in a bush and get FB easily. Definitely not viable in higher elos, and I wouldn't dare try it in ranked, but a shit ton of fun vs stupid enemies, and her damage is surprisingly good, with a 60% ratio on traps (which can be stacked 4 times if used correctly) and an 80% ratio on her e. Not to mention that she provides some pretty amazing poke and her ult base damage is very nice. If teamfights are coordinated around her traps she is surprisingly useful.
I don't play elise support much anymore, but back when DFG was still in the game (I like full AP supports, can you tell?) She had some very nice burst and provides some pretty nice poke, and decent cc and kiting (with rylai's)
Was obsessed with cass support for a little while, her poke is at a level close to vel's IMO, and support cass stacks her passive WAY faster than a midlaner who will be focusing on CSing rather than poking. Her zoning is amazing, and after 6 her cc is pretty decent and her all ins are pretty good once you get a tear. Her passive also helps you out with damage since as a support you shouldn't be building ENTIRELY AP.
I suck at Lissandra, but I've always loved the IDEA of lissandra support. She has SO MUCH utility, and her passive definitely helps you not to waste mana but still be able to poke. Her engage potential is very nice, and when facing a full support support with no damage, she can completely shut down the enemy ADC with her ult and assist her ADC in getting a double kill. She also has some nice surprise ganks when returning from laning or warding.
Maokai is honestly a little bit outshined by Leona, but Mao can actually build full AP and actually do damage. Also, like Caitlyn, he can easily stack saplings to get an easy FB or lategame a 1shot. His poke is okay and using his ult to give you ADC some resistances is nice.
Very good zoner, but usually at the detriment of his ADC's CS. He is also very easy to gank, and his turrets have rather small amounts of HP. But his poke is quite nice, and his all in isn't bad at all.
Sejuani has always been one of my favorite tanky/ap supports. She can still build full ap and end up with a lot of resistances thanks to the many AP/mr or AP/armor and AP/health items. She does very well with Lich bane, and I used to love DFG on her.
Her engage is very nice, but she really doesn't have any poke at all, and she isn't an AMAZING peeler, but she does deal with towerdives quite well, and can in turn towerdive well herself.
She isn't the greatest of AP supports, but she has nice poke, and she does have more utility for her ADC than most other "midlaners" playing support. He cc isn't great, but she has great wombos with a lot of ADCs like graves, MF, and Varus.
Syndra often does very well in laning, but most games I've played with full AP support Syndra I have lost, mainly due to me becoming far too cocky and not thinking through my actions and playing safely. But she does have some very ncie poke and utility, and her cc is nice, especially when using E after an ult.
Nautilus is a beastly support, I'm honestly surprised I haven't seen more nautilus supports. His CC is practically unrivaled, he has a surpression/displacement (his Q) and a built in root on his AA, as well as a nice AOE slow that can be used for poking, and a unique knockup ultimate. He also has AP ratios on all of his skills, so he can be played full AP, and des very nice when build AP, like sejuani and maokai, he can build tanky and AP at the same time and do good damage and act as an offtank for the team.
Zac's AP ratios really suck, so he's best built as a tank. His engage from an unwarded bush is very nice, and his poke isn't horrible as far as tanks go. His passive can also be very useful in bating your enemies into a bad situation, and possibly allowing your ADC to pick up another kill, or keeping the enemy from doing so.
Xerath is a super nice support IMO, but the recent nerf to his stun duration at full range is kind of a detriment to his utility. However, his stun is still surprisingly long, and his poke is amazing. Just be careful not to steal CC from your ADC.
I absolutely hate seeing
and
support, (although cho is actually pretty decent as a support) but they too can still be played decently as supports. I generally just get bored of playing super passive supports, and I've never been a huge fan of Leona or Thresh, and I really enjoy ripping ADCs apart with full AP builds. But generally if my ADC wants me to play as a certain champion, (or not to play a certain champion quite often in my case XD) I will (or won't).
Edit: (Holy I just realized how long this was