On death of a mob, I can open a GUI but how would I incorporate a GUI in which shows random items the mob had dropped (I have a drop script already btw) and so you don't physically have the item in your inventory until you click on the GUI button for the item you want.
If not I could delete the script if it's not usable for a GUI.
I was already given help thanks RockerCaleb, so here's the drop script
1 local items = {"common","common","common","common","uncommon","common","common", 2 "common","common","uncommon","rare"} Then say whatever happens, and they are going to get the item
local items = {"common","common","common","common","uncommon","common","common",
"common","common","uncommon","rare"}
local chosen = items[math.random(1,#items)] -- gets a random one from the list
print(chosen) Then just if the item is common then whatever, elseif it is uncommon then whatever, elseif it is rare then whatever.
local items = {"common","common","common","common","uncommon","common","common", "common","common","uncommon","rare"}
local chosen = items[math.random(1,#items)] -- gets a random one from the list
print(chosen)
if chosen == "common" then
--Do whatever you want
elseif chosen == "uncommon" then
--Do whatever
elseif chosen == "rare" then
--Do whatever
end

2 comments
You can add inventory to every dead mob, and items can get placed into that inventory. Then, when mob dies, a clickdetector gets added in bodyparts, and when player clicks on bodyparts, player will be able to view mob inventory. By clicking on items, items will get added into player's inventory. If you do not know how you can do this, post a comment and I can send an answer with some codes.
I think I could do all of that except making a inventory. Would I use a value for each item in a model or...