I always liked Wonder Girl - well written character, strong, steadfast the team's rock & heart. Simple but classic costume too.
As for NTT villains, my favourites were The Brotherhood - Houngan, Warp, Plasmus, Phobia.
NTT #29 was my first issue - in fact that with about a dozen other DC comics (amongst them Arion, Arak, LSH, All-Star Squadron) which I picked up at the same time were the first DC comics I ever read, in fact ever saw. Never used to see DC stuff in the UK and suddenly one month, my local newsagent had a pile of them. I was blown away - I'd read Marvel before, in the form of UK black & white weeklies and the US 4 colour stuff had just started to appear but I'd never seen DC before. Absolutely loved it and was hooked from then on.
NTT is one of my absolute all-time favourites. It's almost depressing to read them now - there's just nothing today that compares to it. So very good.