On a lot of these interfaces, i put simply nothing.
I do put loctite on bottle cage bolts, then tend to rattle with vibrations. I had to put loctite on the bolts on my non drive side crank arms, because Racework carbon crankets with a crap design.
I would also put loctite on chainring bolts, because creaks develop there.
i would also put Moly silicone thing (as per my recent post somewhere on the forum) on PF BBs, as recommended, apparently, by cannondale, who invented creaking BBs.
Loctite on saddle bolts would also make sense if you're happy with your fit, because they tend to creak too from getting loose.
I've also use a combo of grease & carbon paste on the seat clamp of certain bikes (grease on the thread, and carbon paste on the bit that's pushing against the seat post. In fact it's important to put grease on that thread because sweat tends to get nasty in that area.
Very important: loctite on garmin mount bolts, otherwise they can fall off very fast.