1. Adaptor for Irish Sockets
Unless you are only traveling from the UK you will most likely find that any electrical goods you bring to Ireland won’t work, simply because the plugs don’t fit. Adaptors are available for a relatively low price, so bring your own. Only the variety with the three massive prongs will fit. And take note that Irish electricity runs at 230 Volts - instantly frying all appliances geared for 110 Volts not using a transformer.
2. Rain-Proof Clothing
The Irish weather almost always comes with a rain guarantee. So be prepared and bring some clothing to battle the elements. A relatively light-weight jacket you can wear over other clothing would be ideal, combined with a hat or cap. Umbrellas are cumbersome and tend to die sudden deaths in the wind.
3. Camera
Even though most bookshops will supply a cornucopia of excellent illustrated books on Ireland, snapping your own pictures is a must. A small, light camera with a optical zoom is ideal for most tourists. Remember to bring enough storage media or film, both can be comparatively expensive in Ireland. Also try to use rechargeable batteries only, you’ll help the environment and save at the same time.
4. Travel Health Insurance
A comprehensive travel health insurance is recommended - if only to get the best possible care in the shortest possible time. The Irish health system can be sluggish and extra costs may be incurred if you are pressed for time. If your insurance also covers a possible repatrion flight this is ideal. Visitors to Ireland from the European Union and Switzerland should bring their European Health Insurance Card (EHIC) in any case.
5. Euros and/or Pounds
It is a very good idea to have some ready Irish or British cash on you the moment you arrive, if only to pay for the airport bus or taxi. Or to buy a coffee. Take note that the Euro is used in the Republic, the Pound in Northern Ireland. Both currencies may be accepted occasionally - foreign currencies like the US Dollar most certainly will not.
6. Sunblock and Sunglasses
This may contrast with the rainproof clothing, but the Irish weather caters for every taste. And decent sunblock is hard to find and fairly expensive. Especially remember to put on sunblock when hiking in a breeze near the sea or in the mountains, you can get easily burned here. Sunglasses are a must if driving - the sun can be low for ages.7. Good, Comfortable Walking Shoes
If you are visiting Ireland and want to see attractions close up you will have to walk, sometimes considerable distances. Take your most comfortable walking shoes and step out. Many rural attractions will involve walks over natural, sometimes rough ground. So a sole with a good grip is essential.
8. A Warm Sweater
Even on a hot summer day the evenings can get chilly, take a sweater and be prepared. This may also be of use in some accommodation - many B&Bs have a heating system that only accepts two settings that should be called "Arctic" and "Dante's Inferno" respectively.9. A Good Travel Guidebook
Even if you are joining an organized tour, a good guidebook to Ireland will fill in some blanks. Or induce you to an interesting detour if you are following a recommended route. And it can double up as a souvenir
10. Condoms
If you are planning to be sexually active in Ireland at all (and this will not involve your usual partner) - take precautions and bring condoms. Though contraceptives are no longer illegal in Ireland they occasionally can be hard to find and are expensive. And sexually transmitted diseases are very widespread in Ireland, so "the pill" or a vasectomy are not enough protection.