Jiraiya gets my vote as well, Sage mode put him on another level in terms of Taijutsu and the amount of damage he could withstand was crazy (as illustrated by Naruto falling off that peak). Had he fought Orochimaru at 100% and in Sage mode, then it would have been a phenomenal battle in which Jiriaya would, imho, come out on top in.
Orochimaru's power was mainly from his high level jutsu's, he killed the 3rd, but only because he was an old man and Oro had a fool proof plan. If Jiraiya was around the plan no doubt would have been foiled and Hiruzen wouldn't be gone
Tsunade isn't anywhere near the 3 power wise, she's a medic. Jiraiya's power in Sage mode easily bests her powerful punches (frog katas 4tw).