If going to US, the buses of my choice would be the D60HF, D/C40LF and D60LF, LFS and LFS Articulated, Orion V CNG and 3-axle buses (notabily the Prevost X3-45 and MCI D4500).
In Europe, I prefer some modern buses (Volvos, Scanias, MBs and some Setras), but I am focusing in old ones, because of the history that gives to the public view, specially AECs, Leylands, Volvos, some MANs and Scanias.