However, Crunch, there are also times when carrying something openly is expected, but something like a SMG or AR would be too attention-getting.
I tend to split things into four basic situations, which also goes hand in hand with the kind of clothes/armor I wear in those situations.
Casual/Off-the-clock: This depends to some degree on lifestyle, but when you're not working, you don't want to call attention to yourself by being geared up for war. In most cases, a lined coat with a pistol/machine pistol/melee weapon would work here. The idea is look protected enough that you don't encourage random violence, but don't go around bringing attention to yourself. No R or F equipment if you can help it (or at least don't make it obvious).
Formal: Not all runners are going to have to blend in at a high society event, but your face (or anyone with a high or higher lifestyle, really) ought to give thought to it. Armored clothes, or (when 5th edition of Arsenal comes out) fancy armored clothes are a must. For weapons, a machine pistol is really the highest you can do here, but light pistols and holdouts would be more common. For those who do melee, a reinforced cane makes for a solid club, and swords (especially those that have been suitably decorated) and other blades can often be worn openly in some cultures, especially by magic types.
Working: When you're on the job (and you go to the meet ready for the job, if at all possible), this is where you go with your typical loadout and armor, whatever it is. Well, unless you consider your typical loadout an assault cannon or machine gun. Leave those in the car most of the time, since that tends to get corpsec and the Knights on your trail faster than G-Men chasing someone who tried to databomb Zurich-Orbital. SMGs and ARs are really the upper limit here, or perhaps a grenade launcher. Try to leave this at R or lower, unless you can conceal it well.
Heavy Drek: Like the name implies, this is when you're planning for all hell to break loose. Anything goes, just get back alive.