My favorite 8-bit cart style is the modern XL/XE style reproduction used for Laura, Flob, Last Squadron, Scramble, onEscape.. and others. Looks great and fits every 8-bit, including the 800 and 1200XL.
BITD, the Activision carts were amazing for their small form factor, nice grippy sides and large picture labels. Also can't fault the old-school brown/metal Atari carts.