You can throw all kinds of stuff on a weaver rail. Apex barrels are fun.
As for the pilot, here's a few things I did to my Imagine:
short barrel with a Dishka Flash Suppressor (canonizer). It scares the noobs. Again, also get an Apex so you can keep the Flatliners at bay.
Scenario Dreams T Board (with ramping mode)
Kingman ACT Delrin bolt
New grips (Dye Stickies)
After that, everything is cosmetic: