I make TONS of custom weapons for my figures! Heres just a small sampling:
Here is a gallery of custom Star Wars-scale weapons from the Halo series of video games.
First up is my personal weapon of choice, the S2 AM Sniper Rifle:


Parts: Assembled from bits and pieces of almost a dozen different G.I.Joe and Star Wars weapons.
Next up is the M19 SSM Rocket Launcher:



Parts: Middle part of a Wave 7 Bazooka's bazooka, a spear from the "X-Men villian "Ahab", trimmings from several different G.I.Joe weapons.
Finally we have a medly of small arms. The ones on the left are M6C Pistols, and the larger ones on the right are M7/Caseless Sub Machine Guns:

Parts:
Pistols: heavily modded Chap Mei Wild Force pistols and trimmings from a Saga Djas Puhr pistol.
SMGs: heavily modded Episode I Naboo Soldier rifles and pieces from "The Corps" sniper rifles.

I felt that the G.I. Joe character Chuckles was always underarmed carrying just the pistol, so I decided to amp up his firepower a bit for his "Galactic Intelligence: Joint Operations Elite" version. I fugured that a blaster carbine-sized weapon would give Chuckles the extra firepower he needs while not being rediculously overarmed. The carbine is a custom made from some G.I.Joe rifle (Blackout?) I got in a trade last year and a piece trimmed from a POTF2 Stormtrooper rifle.

Here's another "Galactic Intelligence:Joint Operations Elite" weapon- Recondo's rifle. I made this from the oversized "Operation: Aliens" Colonial Marines Pulse Rifle that was packed with the KB Exclusive Vasquez figure. I dremelled out the area inside the carring grip on top and completely repainted the rifle to match the ones in the film "Aliens".


More "Galactic Intelligence:Joint Operations Elite" accessory goodness! This time it's a medical case carried by the team's medic, Doc. It's made from a vintage G.I.Joe "Tiger Force" Lifeline medical case and a POTF2 Mynock Hunt breathmask. Every millimeter of this thing was repainted. The Aurebesch writing on the front cover says "RESCUE" as an homage to the Lifeline figure it came from


The blaster carbine carried by my "Galactic Inetlligence:Joint Operations Elite" version of Snake Eyes was made from the rifle that came with the Joe named Bullhorn. I just cut it up into little pieces and glued a few of them together



These "Brotherhood Of The Serpent" baddies are carrying custom staffs. Cobra's is made from the top part of a G.I.Joe Venomous Maximus staff and most of a Weequay pike. Mistress DeCobray's staff is the top of an "Aladdin" Jafar staff and the majority of a Chancellor Valorum staff.

The gun carried by my "Brotherhood Of The Serpent" version of Destro is made from an "Armor-Tech" handgun and some odss'n'ends.