The late Les Moxon G6XN in his book HF Antennas for All Locations (which you really should buy) describes two loops, each with tuned feeders coming into a shack via a switch box. To change direction you swap the feeders and tune the parasitic element via the unenergised feedline.
Anyway here are some ideas from others who have succeeded with them.
* Rick C's reversible yagi for 20m
* AA2NN's reversible yagis or 40m
* AC0C wire phased v-beam for 40m
* M0MCX bidirectional switchable wire yagi
* N4JTE 2 element reversible quad
* N4JTE reversible string beam
* 2 element fixed reversible yagi for 20m
* W4RNL's antenna options - 14 Reversible wire beams for lower HF use (pdf)
PS: Wish to explore other aspects of amateur radio? This top selling book is full of ideas. Available for $US 5 in electronic form with a paperback edition also available it's ideas for both the beginning and experienced ham. Find our more here.