I love the rules in the 'Weapons and Arenas' from Old School Hack. This is a mod for Tunnels and Trolls inspired by the same rules (arena descriptions are taken straight from the Old School Hack beta rules):
Tight Arenas: Narrow Places that often limit your mobility somehow.
- All daggers and swords that are 2 1/2' or less gain up to a 1d6 bonus in adds determined each combat round (easy way to do this is to have a colored bonus dice assigned for each character that counts as a regular combat die but also serves the function of determining the bonus)
All hafted weapons, swords that have a weight of 150 or more as well, or polearms suffer a 1d6 penalty while missle weapons suffer a 1d3 penalty(1d6: 1-2 =1, 3-4 = 2, 5-6 = 3)
Hazardous Arenas: Places where footing is difficult or visibility is limited and requires care.
All swords 6' and over, spears and pole arms(including quarterstaffs gain a 1d6 bonus(determined by same method above)
daggers and swords that are 2 1/2' or less suffer a 1d4(d6 -2, most likely will receive a 1 for penalty) penalty.
Open Arenas: Stark, wide-open areas where there is little to no cover.
All Missle SR roles gain a 1d6 bonus (again determined by same method above)
Dense Arenas: A crowded environment that has lots fo fiddly but smashable bits that might get in the way.
All hafted weapons and swords that have a weight of 150 or more gain a 1d6 bonus(again determined by same method above)
missle weapons suffer a 1d4 penalty (d6-2).
Neutral Arenas: A bland or ambigious environment that's hard to define. Most arenas are this.
Missle weapons gain a 1d3 bonus if in neutral arena and outside
Middle sized swords, and all other weapons not mentioned receive no bonus or penalty. Daggers and small swords have a bit of an advantage in balance but that's because they deal much less damage.
I like this for the same reason that I like this OSH - it give some more strategy in weapon selection and allows for more varied combat.
The brilliance of T&T combat is that the division of damage makes combat easy to narrate. This is true of bonuses added especially when determining the bonus or penalty each round. For example:
Round 1 using my dirk in a tight space such as a goblin's small barrack room.
If I roll a 5 and succeed in my combat roll then I could describe it as: "I roll beneath a table, leaping out and stabbing the Goblin in the legs as he runs past the table toward Glain the dwarf.
If a 1 is rolled then I could describe it as: "as I grapple with the orc on the ground, I just barely find a way to plunge my dirk up under his chest plate while keeping the tip of his broad sword away from my body." (basically the degree to which you are successful with your bonus can be used to narrate the degree to which your bonus works for you in your combat round)
Or if using my Sling in the same situation, losing the combat roll, and I roll a 3 on my penalty: "I try to retreat a few steps to get some distance then I release a shot directly at the goblin behind the bunk, but the goblin swiftly hides behind the bed's headboard and the shot flies directly over his head."
Since T&T combat rounds are essentially 1-2 minutes depending on your combat bonus, it's then easy to describe your movement and position in the room like if Glain rolls a 3 bonus with his Sax then he could describe his action as "I move away from the door, running over to the table, leap on top of it, then jump on top of the Goblins back stabbing him in the neck!" The table then becomes an advantageous set piece in the encounter and can be used to describe amazing attacks.
You're essentially justifying the dice results through the narrative and the T&T longer rounds(1-2 min) give you more freedom to describe what happens.
It is optional whether you decide to give monster bonuses or not. If so, I think it best to only apply them in the occasion where it is obvious for example: goblin archers in an open arena, giant troll in dense arena(bar fight) etc. If playing solo this obviously could be phrased as a question in Mythic (Will the trolls size be an asset to him in the bar fight? - answered as a 'likely' question)