I also like the Tavor. http://world.guns.ru/assault/as30-e.htm
I've got a cousin in the IDF who wants to take the compact version CTAR-21 the next time he gois into a PA city. The barrel is just over 15 inches long. Moreover, the bullpup design keeps the entire riffle less than 26 inches long.
The HK MP-5 is only 20 inches long.
The HK53 is also a cool soutions. It looks like an MP-5 with 5.56 ammo. http://world.guns.ru/assault/as13-e.htm