You can't go to Dublin without having a Guinness - sorry, I don't make the rules. The Guinness Storehouse is a fun experience for Dublin visitors. The self guided tour covers the history of Guinness and for the price of admission you get one (correctly poured) Guinness (and enjoy it overlooking Dublin)
Temple Bar is a classic Dublin experience. It is a touristy area with pubs (the most famous is pictured above) and live music. It doesn't hurt to be a tourist sometimes :) Temple bar is also a great central area to stay in while visiting Dublin.
The Jameson Distillery is a great experience for Whiskey lovers (and Whiskey tolerators). Unlike the Guinness factory tour, this tour is guided and is very informative but only lasts about 45 minutes. With the price of admission, you get a cocktail and you get to taste three whiskeys. Would highly recommend as we had a great time there this past winter.
Founded in 1592, it's the alma mater of writers like Swift, Wilde and Beckett, and its 16 hectares are an oasis of aesthetic elegance. The biggest draw is the barrel-vaulted Long Room in the Old Library. It’s the home of one of Ireland's greatest cultural treasures, the Book of Kells, the beautifully-illuminated Gospel manuscript that dates back to the 9th century.
The Cliffs of Moher are a can't miss when visiting Ireland. I would recommend booking a bus tour! It's a bit of a hike from Dublin, so expect this to take one full day. I've visited the cliffs twice now and although its a long drive, it's worth it. Pro tip: if you decide to drive there on your own - the country roads can be narrow and scary at times, but we survived it
If you have 90 minutes to spare - we would recommend a walking tour of Dublin. There are a variety of companies that have these - we used Viator (linked below). It's a fun way to learn about the history of Dublin. Pro tip: bring an umbrella. Hop on hop off bus tours are also common, if you don't want to risk weather or have challenges with mobility.