There are various beautiful national parks in Malaysia. There are many different types of expeditions available, ranging from those where you hardly lose sight of the hotel to those where you are fully immersed in the jungle with only the guide and yourself if you are willing to pay the money! Tours vary from about 4 days to 2 weeks or more. It is very unlikely in most of the national parks for you to see a tiger or an elephant as it is really likely only if you are going to be staying for longer than a few days, i.e., for a couple of weeks at least. One of the most common forms of wildlife that you will encounter in the jungle, however, are definitely leeches! In the rainforest it is very, very humid but actually it is not incredibly hot. This is because of the large amount of shade afforded by the canopy created by the interlocking trees. Shop around for deals of getting into the jungle and make your decision based on what type of person you are. If you are going to enjoy a lot of hiking without seeing any other people for days or even weeks then you can have that choice, alternatively you can have a much more 'packaged' tour in which you will probably stay in a very built up tourist town which has probably just grown out of the demand for people wanting to stay in the jungle.
To escape from the muggy tropics, do as the English did and head up to the cooler highlands of West Malaysia or climb Mount Kinabalu in Sabah.
Malaysia is also well-known for some pristine beaches with great diving opportunities, such as Sipadan off the coast of Sabah and the Perhentian Islands, which are off the coast of northern Terengganu. Coastlines in the less industrialized parts of the country, in general, are well worth driving through for their natural beauty and relaxing seaside kampung villages, though beware not to swim at any beach which is not protected by capes, lest you be swept away by a powerful undertow.
If zoological exhibits are more your thing or you are visiting with children, there are several well-maintained zoos all over Malaysia that are worth a visit or two, most notably Taiping Zoo, Kuala Lumpur 's Zoo Negara and Malacca's Zoo.
If you are most interested in taking the pulse of a city, Kuala Lumpur's crazy quilt ultra-modern skyline, including the famous Petronas Twin Towers, is worth visiting. Ipoh may be of more interest if you prefer a somewhat slower paced city that features elegant colonial-era buildings from about 100 years ago, and Malacca is for those who want to trace the colonial and imperial history of Malaysia several hundred years further back. Penang is known for its great food and relatively long-standing and institutionalized Chinese and Indian communities, who share the city with Malay and Thai communities. For a completely different experience, consider going to Kota Bharu to discover a unique conservative Islamic regional culture influenced by Thailand, only a few kilometres away, or visit the diverse cities of East Malaysia, like Kuching and Kota Kinabalu.