If video transmission gear needs to be light, its good to use high frequencies, because then antennas are small. 5.8Ghz is the most popular band to transmit video from a micro RC model, and clover-lear (circular polarised) antennas are by far superior to the traditional linear antennas.
Circular polarisation can be achieved in both directions, left- and right-turning. Use the same direction on transmitter and receiver, otherwise the signal will be much weaker. This can be an advantage when flying FPV together with others, by using different antenna polarisations to minmise interference.
Here are a few examples of micro CL antennas for the (micro) transmitter:
TrueRC micro CL, no connector, $20: http://www.truerc.ca/shop/antennas/5-8ghz/nano-clover-leaf-diy
Looks light and sturdy.
TrueRC micro CL, u.FL connector, $30: http://www.truerc.ca/shop/antennas/5-8ghz/nano-clover-leaf
Oversky CL, u.Fl connector, 6.19$: http://www.banggood.com/Oversky-5_8GHz-Circular-Polarized-Antenna-LHCP-RHCP-Set-RP-IPX-p-1000576.html
Banggood CL, no connector, 3,99$: http://www.banggood.com/FPV-5_8GHz-Micro-CL-TX-Anternna-0_8g-Lightweight-p-973291.html
multiFlite CL, u.FL connector, 15$: http://store.multiflite.co.uk/index.php?route=product/product&path=63_64&product_id=68
Very lightweight, long cable. Fragile without epoxy coating.
ultralight Cloverleaf Antennas http://www.red-leaves.de/larot-avionic-5-8-ghz-fpv-antennen/cloverleaf-ultraleicht/
Realacc Mini 5.8Ghz 3dbi 1cm 4 Leaf RHCP FPV Antenna for Blade Inductrix Tiny Whoop http://www.banggood.com/Realacc-Mini-5_8Ghz-3dbi-1cm-4-Leaf-RHCP-FPV-Antenna-for-Blade-Inductrix-Tiny-Whoop-Eachine-QX90-X73-p-1090770.html
5.8 GHz Micro CL antenna 1 gramm http://fpvhobby.com/240-ghz-micro-cl-antenna-.html
If you know of other antennas, please edit this post and add them to the list!