Depends what "style" of combat you're going for, I guess. If it's a more "vanilla" style, I would say no to any guns, tanks, war machines, etc.
So, I'll say that my opinions on combat here are purely based on a more "vanilla / medieval" style of combats, although with a little bit of Minceraft's weirdness thrown in.
Dual wielding should be a thing, allowing for sword / shield combinations and the such.
- When a player is using a shield (probably with a sword), they're able to block all damage from the direction they're facing. It seems a bit overpowered.. until you realise the other changes I'd make.
- Most weapons have an amount of "stun" which is different from their usual damage, determined by weapon type. Minor stun will not stop a player shielding, but major stun WILL - while the shield will block the attack which causes the initial major stun, this leaves the previously shielded player open for further attacks. Stunning will only last between 0.3s-0.6s, so a single player won't be able to "stun-lock" an opponent. With this new stun system, regular damage should NOT deal any form of knockback. It's annoying enough suddenly plummeting downwards when hit by poison or drowning, and it makes no sense whatsoever.
- Most weapons act differently depending on how they're "charged" - simply clicking with a sword will trigger a "jab" with low damage and minor stun, while holding down and charging a sword will trigger a "slash", with greater damage and major stun. Note that getting stunned will drop your charge, so jabbing a charging player is a good way to stop them slashing your face. Weapons should also be unable to just be "rapid-click spammed", most attacks will have a 0.2s-0.4s "pause" after the attack, as a sort of cool down. Jabs would have a shorter cooldown, while slashes would have a larger cooldown.
- Bows in vanilla are a bit TOO powerful and spammable - bows should take much longer to charge, and be unable to fire unless at at least half-charge. A fully charged arrow should deal major stun.
( Yes this may or may not be heavily based on the game King Arthur's Gold whatever )