I am using Bajaj Discover 125 cc engine bike and very much satisfied with its performance. Mileage is the key part for this category of bikes and Bajaj discover 125 scores full in this category. It gives mileage around 60 km per leter in city trafic which is very well.
Design and look wise also its good. Engine life is also long and there is not much maintenance. Just take care of regular oil change and you never have to ask for maintenance. Pick up is aslo good in its category. Under 50000 this is one of the best option available.