From a strictly dog behaviour/character POV: Great Dane
Had one once (and so gotta know many others), theyre the probably softest and most obedient dogs I have ever come across (only have one problem from their POV: How do I get on the lap of my boss :-??). You can leave them alone in any place, they won´tmove, you trip on them, they won´t bite, for some time I thought they didnt even know how to growl or bark...
Until one night, when I got attacked by a few skins in the woods (and my dog nowhere to be seen), when he suddenly came like a monster flashing straight out of the dark with a malicious growl and went straight for them, never have anyone seen running so fast (one was shouting: "A panther, a panther...!" :mrgreen
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OTOH, from a practical POV, they re just too big, do not fit under any table, need lots of food (mine, at 90 kgs downed 3kg of meat every day...) and people get easily afraid just by seeing them.
Rattler