You start with a very limited number of weapon proficiencies that are provided by your race as specified in the PHB and a certain number provided by your class (homebrewed). You can pick any weapon proficiency you wish. Every entry in the weapons table corresponds to a weapon proficiency. We disregard any reference to 'simple' or 'martial' weapons.
All weapons and armors can be purchased at 4 different qualities: poor, normal, good, exceptional. Price is adjusted and better quality corresponds to certain perks. Armors can go down in quality when upon receiving a critical hit. Weapons can go down in quality upon fumbling an attack roll. The cantrip 'mending' can be used to repair although some spell slot may have to be expended.
I have written a set of multiple rules which cover engaging a melee opponent. These rules punish characters involved in fighting multiple opponents and favors pack tactics.
You can move around an opponent without triggering attacks of opportunity as long as you remain adjacent to him.
I wrote fumble charts for magic use (about 50 for each school). Whenever you use magic, roll 1d20 first. On a 1, you fumbled. Roll on the appropriate chart. On a 20, you roll on my custom critical chart (its not necessarily double damage die if it's a offensive spell).
I also wrote fumble / critical charts for initiative and melee + range attacks.
Initiative is rolled every turn.
There are magic wands for arcane casters, holy symbols for divine casters and totems for druidic casters, all of which work slightly differently but, in essence, allow casters to buff their spells (either on range, number of targets, damage, etc.)
I'm currently working on a set of rules which will frame the ''hide action'' in combat. I am not a big fan of rogues hiding in plain sight in the middle of combat. I intend to allow it although in a very contextual sense. This is still work in progress though.