Great Topic!!
Although every map has something special in it and I love to play in all, I would give my Top 5 here :
My picks are :
SLUMS
My favourite map in the game. The narrow alleys, the rooftops and such other factors make it a really interesting and unpredictable maps in RT...
OPERATION EGYPT
I think this map is quite unique as well... Rushing around with a sniper and quick-scoping gives no more fun in any map than this..
URBAN WAR
Of course, the classic map of RT... How can I miss this one... If you want to find the hardest players to beat - get here...
WAREHOUSE
A really good map with a closed and compact design... You can't jump around here as much as other maps, you can't camp too long... And my ideal map for playing Bloody Mary!
DE_DUST
This is another map I love to play in... A large fort with end number of options...
I missed out some like Assault, Snowoot, Chapelle etc. but I had to choose just 5...