There are a number of good places to visit in Karnataka like Nandi hills, Kolar, Chitra Durga, Shivasamudram, Shimoga(Jog falls), Chikmagalur, Bandipur, Kabini, Gandhikota, Lepakshi, Talakaveri, etc.
There is many best places in karnataka. Few listed
1. Hampi - Historic Places
2. chikkamagalur - Hill Station
3.Coorg - Hill Station
4. Mysore - City, palace
5. Gokarna + Murdeshwar - temples and beach
6. Dandeli - Water sport places and hill station
7. Bijapur - Forts
Costal karnataka like gokarna, Murudeshwar, udupi, kumta if you are beach lover.
Hampi, Badami, Aihole and Patadakkal if your intrested in history and architechture.
Banglore, Mysore, ooty all time hit...
Coorg, chikmaglur, shimoga