Just as an example here are some titles, the initial percentage off and the resulting price.

F1 2010 50% - $19.99
Battlefield Bad Company 2 66% - $6.79
Fallout 3 (Game of the Year) 33% - $20.09
The Deus Ex Collection 85% - $2.99
LEGO Batman 75% - $4.99
Peggle & Peggle Nights 60% - &7.99
Prince of Persia (Franchise) 75% - prices range from $2.49 to $7.49 (no bundles, unfortunately)
Portal 75% - $3.74 (If you own Half Life 2) 85% - $2.25
F.E.A.R. (Franchise) 75% - $9.99
Titan Quest Gold 75 - $4.99
Super Meat Boy 75% - $3.75