As Sarge & Ineti have mentioned, swords can be very deceptive in weight. "Nancy" is a 36" folded Katana that can cut through just about anything (including falling silk), however, she is insanely light to the point that you can easily over-weild her and get knocked off balance by your own strength.
If a sword is too heavy (any weapon really), the one weilding it will tire too quickly and become too slow in combat. Armed combat is fierce enough, let alone when you've got a sword that's too heavy and making your shoulder ache to the point of wanting to take a knee (which will probably result in having the head removed from the body free of charge).
A buckler, depending on the era, can be something that just belts onto the forearm to keep daggers at bay. Normally just covers the arm and not much else. A small shield would give you a bit of cover for the head (if raised) or torsoe, but normally not both. Large shield, gives decent cover to torsoe and head. Tower shield is pretty much a walking wall - better be Ahnold if you want to enter melee with a tower. Nice spiked small shield can double as a bash weapon. Weight also depends on the material: wood & leather = pretty light (unless walnut). Steel = a bit heavier, depends on size of shield.
War-hammers and maces --- which always tend to get a "heavy" weapon classifier normally were not much heavier than your normal ball-peen or claw hammer. Something that you could swing all day long and not get tired of using. I use 8 - 32 lb. sledges and mauls along with 2 - 4 lb. axes ---- I can go with the axe for 1/2 a day, but the 8 lb. maul normally I have to take a break after only 20 - 30 mins. The 32 lb. sledge is mostly just for overkill fun and display, if I were to use that for combat, I'd be knocked out of combat before I even got the first swing.
One of my favourite weapons was a 4' long "Demon Slayer". Looked heavy as hell and bad-ass (Conan woulda been proud). However, it was incrediblly light (almost threw it over my head when I went into combat stance).
Rapiers and fencing swords (unless of course you're Rob Roy and fense with a broad sword) only go 2 - 3 pounds, if that (not that I've put them on a scale, but the 5 lb. plate feels heavy compaired to them). Can go for long periods of time, but don't do much damage (not intended to do much damage except to honour).
Speaking of honour, I still have an issue with code of honour = flaw. I can see how not wanting to be underhanded can bite you in the butt in combat (I won't hit him while he's down, but he won't hesitate to do the same to me). Just personal opinion on how honour is read. I like the write-up of the character.
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