I feel lost without a tach. I want to add one to my Heritage. I don't mind the ones that sit above the bar clamp, but I really like the looks of my bar clamp with the Harley badge on it.
The one I use is the speedo/tach combination. I put one on both of my Heritages and they work great! Just bolt in where the old speedo mounts. They cost about $450, but to me they are money well spent.