Ion Fury: Aftershock

Nearly every level is great—good challenges, full of character—and there are no generic tunnels (except the crypts, which are awful) or facilities (the few facility levels in the game have a great sense of grandeur because they're in and around an active volcano). The first and fourth Zones in particular are easily among the strongest in the entire game (aside from the crypts). A slew of deadlier enemies are well-balanced by new weapons, including alternate fire modes for the shotgun and grenade launcher that add some more much-needed indirect-fire options. Even the vehicle sections are solid, a Water Hazard/Highway 17 mashup with actually good controls (aside from a few really tight jumps on the race level). All-around an outstanding expansion pack.