Some of the tools that i use on a daily basis to make my life easy,most of these are freeware.
i) SQL Sentry Plan Explorer : Best tool for viewing execution plan. Free version gives you all the features except posting the plan in anonymize form and directly lets you open the plan from SSMS into Sentry instead of saving it and opening in Sentry ( i have the full version, got it for a very good price from local SQL Sat event ).
ii) SQL Pretty Printer for SSMS : Good tool to format sql code in SSMS. Free version is pretty good.
iii) Greenshot : Free tool for taking screenshots .
iv) Diskspd : Excellent tool for bench marking storage systems. This will help you in understanding boundaries of the storage system.
v) Hammerdb : Amazing software for benchmarking sql server instances with similar data patterns.