1- Michelle Kline at the University of California had to improvise a material to build microfluidics chambers when her funding dried out. She turned to Shrinky Dinks, and created a low cost alternative!
2- Ellie Wollman and François Jacob had to improvise a way to look at bacterial conjugation and to map the genome simply by measuring the time of transfer. But they needed a way to abruptly stop conjugation, so they use a blender to sever the pili and stop the transfer!
3-Hans Spemman was studying embryology in the 1930's and one of the questions of the time was if every cell has a deterministic fate from the first division on or if they acquire their fate later in embryo development. To divide a cell before it's first division Spemman used a baby hair (since they are sturdy yet very fine) to cleave the cell. In fact just by using this technique and tweezers he was even able to do nuclear transfers and kickstart the study of stem cells. Talk about being ahead of your time.
4-In one the labs I've worked in in the past, we use to cut corners and make our own DNA ladder and our own TAQ polymerase. But Orac takes it further and contemplates how to create your own electrophoresis box. And of course you can make your own DNA columns if you visit the local potery shop, or just reuse your Qiagen columns.
5- Submit your story in the comments, and we'll see if it's McGyver-worthy...