Grimsel and Furka are lovely, old school Goldfinger-like. My favorite ones are the Nufenenpass and the Sustenpass. Both are well known by car enthusiasts also from GB (we've once met a group of Ariel Atoms). I use to drive them fast (within the speed limits of course plus a 'payable' safety margin ) that's why I think that maybe 20 % of the Furkapass and the Klausenpass are a little bit problematic on weekends.