Depends on how much time you have.
you can visit Gandhi mandap to get a good view of the city, try out some local cuisine in " Paradise restaurant", Mising kitchen.
you can also visit the Kalashetra for arts and culture.
If you have around 3-4 hours you can visit Pobitora wildlife sanctuary
You can visit kamakhya temple, Peacock island, Kalasetra, assam State museum, ship cruise among others. you can also visit Brahmaputra river heritage, lush cafe, olive rooftop garden, Tera Maya, khorika for delicious food in Guwahati