Simple wilkinson/gillette* double edged things - currently on a 60s(?) razor but my father's old razor I used for years till the thread went a few years ago (hmmm...wonder if I can get it helicoiled...)
*or whatever's available, some other manufacturers might be sharper/last longer but I've never been fussed enough to hunt around - I shave at anything between twice a week and twice a month. Actually, the mach 3 things aren't bad but don't work very well with more than several days growth or trying to cut around beard and sideboards (I generally have all three). I've actually got a bag of BIC things I bought mebbe 10 yrs ago in desperation...they're bloody awful
Soap...whatever's in the soap dish - even the rubbish foam stuff we have in our office dispensors - just making sure it's well-wetted.
My necks actually a bit sensitive to shaving (or used to be, 3 days in a row in my 20's and it'd be raw..), but doesn't seem to get upset with the above.
ISTR the old dual-edged razors being described as one of the first items of the 'throwaway society'..perhaps one day I'll get around to get an open razor, if I convince myself I'm not going to b*gger it up when stropping it