Obscure ... how do you think Pun-pun happened ??
iirc - there was a thread called Endless Spells,
back on the old CO board,
that recycled APs to produce a loop.
It may have been say around level 5 (?).
That might be why every other AP based trick kinda died after that.
EDIT: Solo posted this on his Truenamer thread:
If cost is an issue for these spells (though I don't see why it would be), you can always save cash by buying a single charge wand of Unfettered Heroism, and the feat Wand Surge, which allows you to spend a single action point in the place of a wand charge. Since Unfettered Heroism gives you back an action point plus one per round as long as the spell lasts, you can gain a net return of many action points which you can use on other wands.
And if this is it, Psionics can do this too (with minor hinkeyness).
EDIT EDIT #2 --- heh, I'm going blind Maat_Mons.