I was going to do a top ten list for both my favorite and least favorite RHATO issues. But I think I've been obvious with which issues I didn't like and I'm have trouble picking my favorites since some issues are back to back in arcs. But there are some characters I'd like to see, not necessarily in RHATO as I think some of them are little out there.
Andrew Bennett (I, Vampire): I loved that series and the feeling it brought. It would be awesome to see Andrew in a supernatural battle again. I know he shows up elsewhere but from what I've seen it's never had that same feel. I, Vampire could be unpredictable and some times Andrew could be too. The sheer scope of him in the midst of armies of vampires, zombies, etc. always felt epic. I haven't seen that captured in anything he cameos in. This is a guy that might be "tame" by vampire standards but he can still be devastating.
Walker Gabriel (Chronos): This is a Booster Gold crossover I'd love but probably will never see. I'm not even sure if most of DC know about his brief series. Walker has a lot in common with Booster in regards to stealing, having a secret family and the series ending trying to prevent a very Mr. Mind like attack. Much like in his series I see Walker as someone who walks the line of being a hero and villain. He does heroic things but mostly is in for himself. Especially if he's trying to survive which could create some interesting conflicts with the Time Masters. They could be friendly too which might be a bad influence on Booster.
Demon Knights: Through time travel we have meetings between characters from present day and medieval. The future person knows who some of these people are and knowing they can't stop Savage, etc. Just having modern characters adapt to a different setting is a gold mine of potential.
Resurrection Man: I'm not too familiar with the character. I think Immortal Man is supposed to be someone else? One of them was in the issue I bought with the Forgotten Heroes where he only came along to die. But he could still be used to great effect as an immortal and someone who did horrible things in his past. How people react to him and how he copes could be fascinating.
Trixie Collins (Booster Gold Vol. 1): Whether or not she's Rip`s mom doesn't matter. Trixie was an awesome character that felt real. She was a country girl trying to make it in the city with a crush on her handsome boss. She was also quirky, said what she thought, empathetic and worried about her weight. The last one may seem weird but it's the reason why she was in shape which usually gets dismissed in comics. She made a client apologize to a cat, saved her boss, saw the value in people most missed and told off the JLI for their behavior. Trixie was just awesome.