
1] As it is now, dungeons with a shortcut back to the surface on the final level (the maze, elven ruins, any dungeon with the rod of recall)
2] Dungeons with non-persistent levels that increase in difficulty on the way back once you've killed the boss, making leaving a trial as well?
3] Dungeons that have a few extra levels after the boss' level which are markedly more difficult than the previous levels, but offer a quicker and more exciting exit?
4] Dungeons where a time limit activates after the boss is defeated. Failing to the flee the dungeon within the time limit could revive the boss and remove whatever artefact it dropped from your inventory, or it could kill you outright. Lots more monsters could spawn on the way out as well.
4a] A "soft" time limit: Once you've killed the boss, your gold ticks down until you escape!
5] Longer dungeons which have "checkpoints" every 5/10 levels or so. Once one is reached you can enter/exit the dungeon from that level from the surface.
6] Bosses that could curse you on dying, giving you a little challenge condition to leave the dungeon under. -5 levels, a constant curse of vulnerability, etc. until you leave the dungeon?
7] A boss that, when defeated on the lowest level, will continue to return and attack you as you leave, with you eventually putting it away for good on the first level. Sus is right, killing a recurring enemy is fun.
