TZ has loads to offer, from Indian Ocean Beaches to world-famous safaris, and more. If you are interested in Safaris in and around the Serengeti, there are direct flights to Kilimanjaro International Airport (Arusha) with Rwandair. We recommend African Scenic Safaris for trips in this region. It is also possible (but long!) to drive to the Serengeti from Rwanda. More info on this can be found here.
For Zanzibar, the easiest and most affordable way to reach the island from Kigali is first to take a direct flight to Dar es Salaam with Rwandair, then book a short onward flight to Zanzibar with Auric Air, Precision Air, Coastal or Zan Air. There are also ferries from downtown Dar but this option usually works out more pricey! Zanzibar has 1,000s of accommodation options, from 5* hotels to beach camping - search on TripAdvisor/Air BnB to find what you're looking for!
The border with Uganda is a short 1.5 hour drive from Kigali. Just across the border is Bwindi Impenetrable Forest, home to the region's largest concentration of mountain gorillas. Gorilla tracking here is much cheaper than in Rwanda. Note that the minimum age to trek with the gorillas is 15 years old.
Trekking with gorillas can be paired with several other activities nearby. Tour operators based out of Kigali can arrange your entire trip across the border. Lake Bunyonyi, "Lake of Birds" in the local language is rumored to be the inspiration for Wakanda in the Black Panther movie. The lake, Africa's second deepest, is dotted with 29 islands. It's safe for swimming and offers stunning sunset views across the islands. Two nice accommodation options are the Bird Nest for a higher budget and Itambira Seeds of Hope.
Queen Elizabeth National Park is about a 5 hr drive north and is home to over 2,000 elephants and famous tree-climbing lions. There are several lodge options in the park and the boat ride down Kazinga Channel is well worth the trip to see elephants and hippos along the bank or to look out for the 550 bird species. The park offers chimpanzee treks in Kyambura Gorge too.