Les Paul Standards are the classic example.
All the ones that are around $800 with an hour to go, suddenly go up to $1200/1300 whereas all the ones that are already at $1,000/$1,100 usually stay at that price.
Theres always several snipers on popular items. And on unpopular items if the snipers just put their bids in early other people would snipe the auctions with less bids.