That's nothing. Try the Death Beam. It deals 99 damage, and is something like the "wide" weapon, except it has an absolutely ridiculous firing rate. Open your save in a hex editor (profile0, profile1 or profile2 in rsc_k\profile) and assuming that your first slot weapon is the Pea Shooter or one of its derivatives change the byte at 0x8DE to 04.
0x8DD represents the type of weapon for slot 1 while 0x8DE represents the level.
These are the possible values:
00=No weapon
01=Pea Shooter
02=Fan
03=Bubble
04=Fire
05=Kuro Blaster
06=Rocket
(Death beam is a level 5 Pea Shooter btw)
There's a weapon slot every 4 bytes from there.
Edit: I found item slot 1 at 0x8CC
00=No item
01=Jetpack
02=Heart Jar
03=Jacket
04=A.. heart icon?
05=Heart bundle icon?
06=Extra heart icon?
07=Extra life icon?
There's an item slot every 4 bytes from there.