When calling down with A high/underpair is OK...
 

Re: When calling down with A high/underpair is OK...
 

I would also add situational/metagame. eg) I've bet-folded the turn in 3 successive hands in the past orbit or so, and I get into yet another HU confrontation where I am c/r'd on the turn. I'll consider calling down if the board isn't too threatening because it's entirely possible that my opponents have started to take shots at me because of my recent folds. you'll be surprised what you see if you take these into account.

Also, I'll take A-hi or an underpair to showdown against LAGy players HU unless the board gets awful pretty regularly.

Surf

Re: When calling down with A high/underpair is OK...
 

When my opponent is an asshat.

Re: When calling down with A high/underpair is OK...
 

maniac opponent