I can name a whole lot from each season: Jason(MMPR), Adam(MMPR, Zeo, or Turbo; I don't care just put him in goddammit!), Ninjor(MMPR; seems very likely as his Sentai counterpart was even in Gokaiger), any(if not, all) of the Aquitar Rangers(they've served a purpose in both MMPR and Zeo), Trey(Zeo), Auric(Zeo; we want to see him more in action), Blue Senturion(Turbo; likewise), Phantom Ranger(Turbo; we still have yet to know his identity/origin), Andros(Space; I mean, come on. He defeated ALL of the evil villains in Countdown to Destruction, how can you not put him in?!), Zhane(Space), Magna Defender(Lost Galaxy; don't you just want to see him once more?), Chad(Lightspeed Rescue), Joel(Lightspeed Rescue), Ryan(Lightspeed Rescue; just because he was an American exclusive ranger, that doesn't mean anything), Jen(Time Force), Eric(Time Force), Cole(Wild Force; he destroyed Serpenterra in Forever Red, what does that tell you?), Merrick(Wild Force; would be interesting to see Zen-Aku returns), Shane(Ninja Storm), Tori(Ninja Storm; she was in Once a Ranger), Cam(Ninja Storm; why not?), Conner(Dino Thunder), Kira(Dino Thunder; likewise), Trent(Dino Thunder), Sky(SPD; would be interesting to see him as the Shadow Ranger since he was promoted to SPD commander as of Once a Ranger), Bridge(SPD; again likewise, him as the red ranger), Kat(SPD; we want to see her morph once again), Sam(SPD), Nick(Mystic Force), Xander(Mystic Force; you know why), Daggeron(Mystic Force; now imagine Jenji returning too), Leanbow(Mystic Force), Mack(Operation Overdrive; just because he's the red ranger), Tyzonn(Operation Overdrive), Sentinel Knight(Operation Overdrive), Robert(Jungle Fury), Dominic(Jungle Fury), Scott(RPM; and get his actor to reprise his role too), Dylon(RPM), Gem and Gemma(RPM), and Antonio(Samurai; only because we just want to see him redeem himself along with the other Samurai Rangers after what happened last year).