For me, it was Full Mana Addict Singed, with the new rework he no longer gains health based on a percent of his Mana, that and 
and he would be surprisingly tanky with a little more damage then you would think.
http://4.bp.blogspot.com/-PKo0-UxkD0M/UAi82DZ1S5I/AAAAAAAAAA0/Zm1loVbp_BI/s1600/mana%2Bbanne5.png
AP Rengar
AP tank Trollplank. Build some AP and CDR, and the rest full tank, and just run constantly. You dealt not damage, but it was almost impossible for anyone to kill you. Critplank was also great when you hit 100% crit chance and just stopped using your sword. Just shoot every minion.
ap mister yi [sg-soraka]
Managot A good amount of damage, shield, you look squishy but you have good armour and maybe mr
also urgot
AD Evelynn. I miss the oneshots with her E.
AD Malz
AP Sion (When his Q used to be a point and click stun that did a million damage).
