Honor

 is a currency in Bloons Monkey City given to players as a reward for winning Monkey v Monkey. Players lose Honor if they lose Monkey v Monkey matches so it is a good idea to make sure you can do the best. Make sure your Bloontonium Tanks are full so that most people can't take out your rush.

It's best to do it to people higher than your city honor because you will then lose less honor for losing an attack, and gain more honor than winning.

Despite its prominence in MvM, its only real use is for achievements that give AP/Game Center Points/Google Play Points. The only other use is just for showing off one's strength in BMC, which is rather trivial. In fact, it is negative in terms of functionality due to you not being able to enter Pacifist Mode (Flash only), as well as having a higher chance of being raided due to the fact you're also facing people with high Honor.