Greetings from Virginia, where I am currently at the Q-bio conference. I've seen plenty of great talks, and one audience member in the front row that slept the whole way through mine (he probably got up early to listen to the Ashes as well).
One talk by David Bruce Borenstein from the Wingreen group in Princeton brought the "Type VI secretion system" to my attention (for a more scientific discussion, see this review). This is a rather dry name for a pretty amazing bacterial weapon. Certain types of bacteria (in fact, quite a lot of them) have a harpoon concealed within their cell membrane that can be thrust into neighbouring cells, allowing delivery of toxic biochemicals. Bacteria use this weapon against each other and more complex organisms such as humans. It is similar to (and components may even have been directly stolen from) mechanisms by which some viruses inject genetic material into hosts.
For me, the interesting thing about this device is the ability to convert chemical changes of proteins within the cell into the rapid motion of this harpoon. For example, how exactly is chemical fuel involved, and how much fuel the cell must use to achieve a certain force? How much of an advantage does this active puncturing give?