Vsauce has a nice look at the absurdities of video game inventories, noting a single GTA V character with all gun slots filled and with full ammo is essentially carrying about 800 pounds of gear:
I have to say, those GTA V characters are lightweights.
In Borderlands 2, a character can unlock a total of 43 weapon slots, and each of those slots could be filled with a rocket launcher. A real world equivalent weighs about 50 pounds, so a Borderlands 2 character with rocket launchers in every slot and full ammo is looking at carrying more than a ton of weaponry.