Senexis

All items unlocked and purchasable
Now fully compatible with Red Dead Offline! Make sure this mod overrides Red Dead Offline and you'll be good to go. Without Red Dead Offline installed, certain Multiplayer weapons will not be unlocked for purchase, in addition to making me sad that you didn't install it. Get it here!
 
In this mod, changes are made to the catalog to allow you to buy and and all items without requirements. This is done by manually going through the catalog file and removing the restrictions put on the items that are locked, by adding them all to a custom menu at the Trapper.

In addition, this makes every item always purchasable at Tailors, Newspaper Boys, General Stores, Trappers, Doctors, Pearson and the Bait store. This means that you can unlock items from those stores whenever you want. Newspaper Boys, for example, always sell every single issue of their newspaper, Trappers allow you to purchase the outfit before having crafted all individual pieces, Pearson allows you craft without needing the Crafting Tools from the Ledger, Tailors allow you to purchase all outfits from anywhere, and more. This functionality is intentionally not made available when customizing guns, at stables and at various barber shops, including the Camp Shaving kit. This is to prevent serious bugs from happening.

This adds a custom menu to the Trappers around the world that allows you to buy any item. Adds multiple categories to the menu you can use. The mod adds a dedicated All Items Menu option in which all options are located. Some pages allow you to use Q and E to browse tabs within them. Please note that due to a limitation in the game, the tab indicated (the little circles) stop updating past a certain point, but the menus still work. Items that are normally not available for purchase have been given a purchase price of $0.01, while any item that already had a purchase price has been left untouched and will cost the same.
 
NEW! In addition to the new custom menu at Trappers, this mod also allows you to sell any item that's located in your satchel by selling them to a Fence. Think documents, key items, unique items, and more. All items that are not intended to be sold will not give you cash for selling them. Any item with an original selling price has been left untouched and will sell for the same everywhere.

IMPORTANT: Purchasing or selling items that are obviously not intended to be used in gameplay either by being cut or not intended to be purchased or sold may have lasting and unforeseen consequences on your save file. I have intentionally left everything in there so that you can have fun experiencing what would happen if you got or removed certain items early, et cetera, but this means there is a very real chance that progression using your save game may be permanently broken. If you are worried about purchasing or selling something that may break your game, do not buy items that are free, are sold for free, have missing text, or display anything weird.

BACK UP YOUR SAVE, YOU HAVE BEEN WARNED!
Installation
Back up your save. There is a very real possibility your save will become damaged by using certain options in the menu. Download and install Lenny's Mod Loader. Make sure it's beta 8 or higher. Extract the downloaded ZIP to the LML folder. Done! Your Red Dead Redemption folder should have a folder LML which contains the all_items_menu folder. Permissions and credits
Feel free to use this mod to learn how to edit the file yourself, but if you do please credit me if you learned something. I don't mind re-uploads of (parts of) this mod, but credits are appreciated. Do not just re-upload the file under any circumstances. Both this version and the one on Nexus will be the only official sources. Do not download the file from anywhere else.
 
Thanks to @LMS for helping with the creation of the mod. Without them, this mod wouldn't be possible.
Thanks to @bolmin for helping out with the Red Dead Offline mod.

Easier Gold Medals
This is a very simple mod that makes it easier for the leisurely folk to get Gold medals in the game for completing missions.
 
This mod does two things and two things only (currently):
Makes all timed challenges complete any time.
Allows you to take your time when completing the missions, take a look around, enjoy the battlefield. Makes it so that failed attempts no longer reset challenges.
Sometimes you just stroll around too much and you end up dying. No worries about lost challenge progress in this case! Note: The in-game challenge text will still mention the original times. This can be ignored as they are not directly related to the actual timers.
 
To install, drop the easier_gold folder in the LML folder. Lenny's Mod Loader beta 6+ is required for this to function properly.