Being a Yelmalian Centaur alone on a HeroQuest and being surrounded by dozens of gorps (No problem, you say, but have you ever seen a Yelmalian cast Fireblade or Firearrow?)
Being a Yelmalian Centaur on a HeroQuest and meeting a mistress race troll with a sense of humour. Having failed my INTx5 (95% chance) I did not recognise her and challenged her to combat, having that particular geas. It was only then that I recognised Kyger Litor herself. (She only bit off my little finger as a lesson - lucky me - it never grew back, either).
Realising that the PC minotaur has just killed the last foe by crushing with his glowing black mace.
Similarly, realising that a Death Lord has just returned to battle through Divine Intervention, tanked up with Shield, Crush, Seal Wound and Berserker just as the final Chaos foe bugs out through his own Divine Intervention.
(In Snake Pipe Hollow) jumping into a pile of ashes to escape an angry giant, only to find that the pile was, in fact, a gorp appearing harmless.
Having, as a lay member of Humakt, found and enchanted a 0 ENC, 10 AP hauberk, becoming an initiate and receiving the geas "wear no chest armour".
Realising that the giant in front of me casts no shadow and that both his head and chest are out of reach.
Realising that the group of dwarfs were not actually throwing rocks at me.