Since almost nobody - even with today's supercharged equipment - can hit a 500-yard drive, the best place to look for par-5 aces are on those par-5 holes that are severe doglegs, or are even a bit horseshoe-shaped. On such holes, an intrepid long-hitter can attempt to cut a corner or clear trees or other hazards in order to go straight at the green, rather than playing around the dogleg in a normal fashion.
Holes-in-one on two such par-5s are known to have happened. One was even recorded with a 3-iron! That one was made by Shaun Lynch, playing at Teign Valley Golf Club in Christow, England, in 1995, on the 496-yard No. 17. According to a 2004 article in Golf World magazine, Lynch aimed straight toward the green on a horseshoe par-5, clearing a 20-foot-high hedge, then hitting a downslope on the other side. The downslope carried his ball to the green and into the cup.
The first-known ace of this nature occurred in 1962, according to the Golf World article. "Larry Bruce took his drive over a stand of scrawny pines on the 480-yard dogleg right par-5 fifth hole at Hope Country Club" in Arkansas, and found the cup.
But there's also one hole-in-one known to have occurred on a straightaway par-5. This monster drive was achieved at altitude on the No. 9 hole at Green Valley Ranch Golf Club in Denver in 2002. The shot was 517 yards in length, and the golfer who got the ace was Mike Crean. This ace is believed to be the longest ever recorded.