This guy was a pretty aggressive TAG, so I was planning on showing down my ace high here.

Party Poker 3/6 Hold'em (9 handed)

Preflop: Hero is SB with , .
7 folds, Hero raises, BB calls.

Flop: (4 SB) , , (2 players)
Hero bets, BB raises, Hero calls.

Turn: (4 BB) (2 players)
Hero checks, BB bets, Hero calls.

River: (6 BB) (2 players)
Hero

I bet. Without the flush he wil likely check behind but will probably call with any piece of the board.

Bet the river. The only hands that beat you here are hands with the or the , or of course that powerhouse .

If he raises you, you're likely beat and can bail. If he calls without the flush, you beat him. A bet there could also represent the , so go for it.

Do you guys call down if raised, or not?

A TAG BB defending, on second thought, I may call if raised. I don't think (if he is a true TAG) he raises you without the or , but that may just be a crying call situation to see it. It may be worth a call.

I fold to a raise.

The BB could be defending with the Tibetian Big Slick, like someone else I know...

Piers is 100% right on this one i think. It is a pretty rare situation indeed when someone that makes the nut / 2nd nut 4 flush on the river is going to check it to you with the intention of raising it, because the 4 flush is such an obvious and scary card that there is too big of a risk fo a check behind. Unless the pot is a big multi way monstrosity where someone with the nuts might hope that some ass in later position will bet a crappie flush and allow him to CR the field, you usually wont see someone check the nuts cuz it is alsmot always goign to et checked behind. Bottom line - if checked to i bet any reasonable (10 or better) 4 flush