None are required, and you shouldn't even need malaria pills. If you're planning to live with wild dog packs in the desert you might like to think about rabies, polio, typhoid etc but if you're just holidaying in beach resorts you shouldn't need anything.
Inoculations are free on the NHS from your GP (with the exception of Yellow Fever which has to be done at a specialist clinic if required). Malaria tablets are not free but your GP will give you a private prescription (Malarone costs around �45)
These days they combine a lot of the vaccines so 5 different vaccines are given in 2 jabs - 1 in each arm. Although nothing may be essential for Tunisia some things are usually recommended and it is best to check with your GP about 8 weeks before you go to get up to date advice.