Title pretty much says it all but I'd also like to add categories to this.

1)All in is >50% of you stack

2) All in is <50% of your stack

Yesterday I PFR'd 5xBB with KK, buddy reraised me all-in and I called (about 75% of my buy-in) and he won when his AQ hit the river.

Another situation, I raised 5xBB with TT and a guy re-raised all-in and I called it was 25% of my stack. I ended up winning when his AJ missed.