Some games lend themselves to mods, some don't. The 2 mods I have done:
Charlie's Angels - I added Pascal's Pi-1 board and turned on all of the 'bonus features'. You simply will not find a mod on ANY pinball machine that gives you as much bang for the buck as this mod.
Pirates of the Caribbean - I changed the ship spotlights to green LED's. The difference was amazing, considering it was merely 2 light bulbs. The ship became super eerie, and the Krakken showed up 10x better during krakken multiball.
My current pins are Lethal Weapon 3 and Whodunnit. Neither of them lend themselves to mods really. I've considered adding a matchbox car armored truck to the Tri-ball shot, but that's about it. Whodunnit doesn't really need anything else, but it does have the sling plastics on the right signed by Barry Orsler.