When you first start challenge mode your weapons will be weak and it will take a while for your weapons to upgrade from the mega to the ultra. Your best chance of easily beating the levels would be to save up for the RYNO 2. This can kill most of your enemies in about two shots depending on size (could be more could be less). It would also be a good idea to buy the shield. This is one of my favorite weapons. When you first buy this gun all it will do is protect you from gunfire. The upgrade to this weapon is extremely helpful. It turns into the tesla barrier and it will zap an enemy when it comes close to you. This can be most helpful when you are going up against the mutated protopet. You can shoot at it with the RYNO 2 without worrying that you will get killed by the other enemies around you. Here are what some of the original weapons can turn into: 1)Lancer - Heavy Lancer 2)Gravity Bomb - Mini-Nuke 3)Chopper - Multi-Star 4)Blitz Gun - Blitx Cannon 5)Pulse Rifle - Vaporizer 6)Shield Charger - Telsa Barrier 7)Plasma Coil - Plasma Storm 8)Miniturret Glove - Megaturret Glove 9)Synthenoid - Kilonoid 10)Bouncer - Heavy Bouncer 11)Spiderbot Glove - Tankbot Glove 12)Mini Rocket - Mega Rocket 13)Seeker Gun - HK22 Gun 14)Hoverbomb Gun - Tetrabomb Gun 15)Lava Gun - Meteor Gun 16)Clank Zapper - ?