A comfy saddle. After yesterdays ride home on my Avocet O2 saddle, & suffering th usual nimb "bits", I today forked out [1] for a Selle Italia SLR xp. Just got back from a short (15 mile) jaunt, & it's wonderful; not a hint of discomfort, longer rides to come very shortly now shoulder (mostly) mended.
I realise saddle choice is very personal, but I can strongly recommend this one.
[1] £55 at Bike Shop, Harrow. Parkers do them for £43 +P&P I now realise.