money.
I started keeping an envelope full of $5 bills.
I always wondered about tipping the ramp guys but whether I am "supposed to" or not, I fly in Texas and it is hot. They tow the plane, bring me water, ask me when I am coming back so they can be available when I return.
There's the occasional back rub...
So I chunk a hundred bucks worth of fives in the console for the ramp crew.
I keep it simple, Other than the tip money, I like to bring a pencil, paper, iPad, lube, rubber gloves, a baseball bat, 2 chickens, my Teen Steam VHS tapes starring Alyssa Milano for good luck, fingernail clippers because f*** the FAA, trash bags, rope, shovel, some scratch and sniff stickers and an anal trainer in case I ever meet EdFred in real life.
Oh and gum. Helps with the ears.