I think that what you class as rare might be better labelled as scarce - there are those songs which get played literally a couple of times, and some never at all, but I still think that any song played just a few times on a given tour is a rarity.

The songs that I heard at the 3 shows I attended last year, which I'd class as rare -

I'd Die For You - Played 8 times in 2008, though it was played 25 times on the last tour. Generally a rarity in the US I think, and played more over here in Europe.

Dry County - This was, of course, brought back on the last tour after a 10 year absence, and played 6 times then and 5 times in 2008. I'd think anyone would class that a rarity - and probably one of the most welcomed ones.

Diamond Ring - Played just once on the last tour and 4 times in 2008, this is another which has been out of regular rotation since 1996. Technically this is more rare than Dery County then.

Last Cigarette - Played more widely on the last tour, due to it being from that album of course, but then just the once in 2008, so for this tour it was a rarity.

I Believe - Played a few times on the Crush and Bounce tours, then a 5 year absence until 2008, played just the once. I'd consider this a rarity - and for myself, and judging everyone else, a very welcomed one. I actually saw a banned at Twickenham (night 1) which said "Have some balls; play 'I Believe'" and then they did it (night 2) so maybe that's how we get requests - challenge them aggressively