Carnage Contest is described as 'free 2D turn-based multiplayer shooter with fully destructible terrain and an insane collection of weapons'. There are three alternatives to Carnage Contest for a variety of platforms, including Mac, Windows, iPad, iPhone and Linux. The best alternative is Hedgewars, which is both free and Open Source. Other great apps like Carnage Contest are Worms (Paid) and OpenLieroX (Free, Open Source).
Worms is a series of artillery strategy computer games developed by British company Team17. Players control a small platoon of worms across a deformable landscape, battling other computer- or player-controlled teams. Represent entire series of Worms games.