My recommendations:

Anivia and ziggs are excellent waveclear mages that can easily stall a game for your team and prevent sieges well into the early and mid game. Anivia has a sizable powerspike in the midgame and transitions well into the late game by providing insane utility and zoning tools when her damage falls off slightly because people finish their MR items. Ziggs has an arguably longer range than anivia and specializes more in poke compositions, but his damage potential remains stronger in the mid and late game.
Kayle is an incredibly flexible champion that can arguably be played in all roles. She can build AD with essence Reaver, AP with Nashor's, as on-hit or straight up mage. She is a scaling monster who you do not want to ever see ahead on the enemy team. Her ult grants her incredible utility if used correctly, and is a very powerful saving grace if she falls behind.
Lissandra was once hailed as a frigid queen of top lane, where her consistent poke, innate durability and nasty anti-melee root really made for a nasty opponent. She's been nerfed somewhat since those days, but she is still a powerful pick with huge play making potential. When ahead she can make for an amazing skirmisher with strong pick potential. Late game and in teamfights her ult can almost single-handedly win teamfights.
TF is considered a mid to late game champion as well. His ultimate is a surprising counter to powerful stealth picks such as rengar, akali, evelynn, twitch and vayne. His gold card is certainly a thing to be feared, and will force your opponents to play safely, making it easier for your team to secure a lead. When behind his gold card is still noteworthy in teamfights, as it's an excellent kiting and peel tool.
Udyr is a super strong pick in the right hands, though it has been made easier of late with people discovering runic echoes on him. He is an objective pushing god that takes a concerted effort to counter when he's ahead, but when he's behind it's very easy to slip into peel mode for your backline as a stun bot in bear stance.
Zyra is a pick I simply don't see as much as I should like. She along with vel'koz provide and insane amount of burst as combo mages, but zyra possesses additional utility that he does not in the form of her plants. In their dormant stage, these plants can serve as little mini wards that grant vision of enemy targets that tread on them. She also possesses a long-reaching, multi-target snare and a huge AoE knockup ultimate that drives your plants to insane amounts of damage.
Lastly, Malphite. A tanky nuisance in this AD-ridden atmosphere with a particular taste for the tears of attack-speed based champions. He's a champion who loves his mid to late game. Once he hits 6 it's game on for him. If he's ahead he becomes even MORE tanky and begins to stack CDR to make use of that devastating ultimate of his even more.