Like Watterstide I use Superior Threads titanium needles 80/12, unless I'm working on lawn cotton or silk - then I use their 70/10.
Based on Bob Purcell's advice I now use the 70/10 when I'm using his Bottom Line thread in the needle.
I've already said this on a different thread - October 2009 is the last time I put a new 80/12 in, and my Bernina is sewing like it did when the needle first went in.
http://www.superiorthreads.com