Asahi Supet-Multi-Coated Takumar 50mm f1.4 with M42 mount and Kiwifotos M42 to M4/3 adapter.
This is one of my favourite lenses and is equivalent to 100mm on Micro Four Thirds. A little soft at f1.4 but excellent otherwise. Feels at least as heavy as my E-PL1 and the weight can help keep it steady. It's almost as big as the M.Zuiko 14-42 kit lens (the first version), if not a tad smaller.
The adapter was 0.07 to 0.08 mm short, making the lens focus a little past infinity. Fixed by adding seven aluminum rings (each 0.011 mm) between the adapter and lens. The adapter adds ~25mm in length.