1trusty 
/ˈtrʌsti/ adjective
trust·i·er; trust·i·est always used before a noun /ˈtrʌsti/ adjective [also more trusty; most trusty] : able to be depended on — used especially to describe a useful too, device, etc., that you have had and used for a long time ▪ I never go anywhere without my trusty pocketknife.
