I'm currently playing through Arkham City and good God! I just got finished with the Ra's Al-Ghul Boss Fight on Hard difficulty earlier in the night. To put it simply; it's one of the best boss fights I have played in ANY video game. The second time you go back into the desert and you're jumped by the twenty clones feels like the finale of Red Dead Redemption where you can actually survive. I know the part where he comes at you with a sword and you're expected to mash the counter button like crazy is a bit contrite but man was it fun!
What other boss battles in the game did you guys like?