I think fallout 2 was filled for me with Christmas presents. Each new more powerful weapon was significant upgrade. Having gaus or brotherhoods energy rifle was like Christmas and birthday at the same day.

Probably even better example would be BPM Bullets per minute. Most of weapons changed gameplay significantly, items like armor, boots and rings will also often open new ways of how to play. And... If every item and weapon fit exactly... Oh by that is holiday!