One of my favourites was “The Burgler who Smelled Smoke” by Lynne Wood Block and Lawrence Block as it featured death by halon extinguisher (one of the Bastard Operator's favourite methods for dealing with IT managers). I also liked “Ice Elation” by Susannah Gregory. In this case I thought the setting – a team of scientists in an Antarctic research station drilling their way into Lake Vostok – made for a more interesting story. Perhaps the finest example of a locked room mystery in the book is “Murder in the Air” by Peter Tremayne in which the victim is somehow murdered whilst alone in an airplane toilet.
By about half way through I became temporarily obsessed with these mysteries. I spent longer than is healthy trying to work out a method for the impossible crime of killing my MD while he was in his glass office in full view of 20-odd programmers. I failed entirely, but my husband did come up with a rather neat method for murdering someone using a central-heating system. The best I was able to do was to come up with the ass-kickingly brilliant title, “Murder on the International Space Station”. Unfortunately I had no idea how such a murder might be committed and solved. If you're clever enough to write the story, I'll let you have the title for free!