No option for Fallout Gold/Platinum? The medals that literally exist to show the world that you got really lucky and got to skip a whole lot of floors?
:(
Voted for Gutt's Heart/Iron Skull/Gambler's Shield. Gambler's Shield requires you to play negatively on purpose(not judging the switches, just randomly mashing them) and since mashing switches randomly can kill you randomly, but probably won't, this is less hard and more RNG. Iron Skull requires specific build boring degenerate play, from what I've heard.
Gutt's Heart...I'm not as fretted about Dragonslayer as some people. But simply getting Dragonslayer, and being able to equip it, probably means you're going to clear on whatever difficulty you're on, given the range of floors it can appear at and how powerful it is. That's not really something that needs a medal, and Dragonslayer wearers already get the entry in their uniques anyways to note that they did it. (And there's another medal related to Dragonslayer, I think.) So ehn, seems kinda trite. At least Cleric Cross means you may have had to swap to a pistol to finish off Mastermind, which is at least a little annoying...