Saw this somewhere else and thought it might be a good shout for a thread.
From an Irish perspective, there's a few obvious and notable ones, but I'm sure I'm forgetting plenty. In no particular order:
1. Vs New Zealand in Soldier Field for our first every victory again them.
2. Vs England in Twickenham for the Grand Slam.
3. Vs Australia and France in the 2011 and 2015 RWC's.
4. Vs France for the first of Schmidt's 3 6 Nations titles
5. Vs Scotland in 2015 in what is probably the best day of rugby I've ever witnessed.
Interestingly, all of those matches were played away from home or in a neutral venue.
From a Munster point of view, all the memorable ones to me came in Thomond; beating Northampton after 100,000 phases, hammering Toulouse, Conway with a late try to beat Toulon and the game against Glasgow the week after Anthony Foley's death.