I have 2 things on my "hot" battery bus:
1) A small 1A fused wire to my multifunction display (I believe this helps from draining the internal button-cell battery in the unit)
2) A 7.5A fused 12v power socket in the cockpit. This socket has proven to be very useful, as it allows me easily plug in a 4A Battery Tender after every flight without having to open any panels or remove the cowling. During flight I can plug in a 12v-to-USB adapter if I need more plugs for powering gadgets (note that they will continue to drain the battery if left connected/charging after flight.) I have separate USB sockets that are on the avionics bus though so I don't typically need to do this.
I didn't actually create a "bus" for these 2 items. Instead I have an 18AWG wire attached to the battery side of the master contactor with an in-line fuse on the engine-side of the firewall to protect the wire, running to the 12v socket. From the 12V socket I attached a wire (with smaller inline fuse) to my MFD.
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