Not Updated For Current Season
The masteries shown here are not yet updated for the current season, the guide author needs to set up the new masteries. As such, they will be different than the masteries you see in-game.
*Mobafire is inaccurately calculating the mana which should be around 3.5k+ and lvl 18*
I like to play my blitzcrank as a dps/survivor where i make sure i utilize his mana barrier. The basic idea is to get a ton of mana so that his mana barrier gives him tons of health, while having manamune turn that mana into attack damage. Then lower his cooldowns a lot so he can spam overdrive and powerfist. Overdrive activates sheen doing double damage, then power fist does double again. Late game you can do around 1300 damage in a couple of seconds with just those two skills. Also, if mana barrier activates, the lifesteal allows you to get a fair amount of health back while your shield takes the damage.I try to save static fields active to silence casters after i pop them up with static field or to interrupt channeling spells (nunu, karthus, fiddle). I pick cleanse to help get out of ganks, and when paired with mana barrier and overdrive you can get out of most ganks. I pick flash to also help with getting out of ganks, but its also good offensively to flash in, powerfist, rocket grab, and another powerfist.
I feel like a lot of people buy sapphire crystal first to help with mana barrier, but it already gives you enough health and the extra mana regen helps with harassing and ganking with rocket grab. Other than that it's just basic early blitzcrank play. Pull enemies into your turrets, pull them away from theirs, and just harrasing a little. While playing blitzcrank make sure when you pull your not pulling them into an ally with low health. Don't get too greedy, as your mana barrier won't be too high until you get manamune. I level up overdrive first just so i can pretty much spam it, and same for powerfist.
Use Rocket grab to initiate team fights and turn 5v5's into 5v4s, but don't get too greedy because you have only a little armor until glacial shroud and pretty much no magic resistance, but between your regular health and mana barrier you should have around 3.5k-4k. Go for both red and blue neutral buffs when you can, especially after getting sheen and life steal. It's a great way to lower cooldowns while waiting on glacial shroud. Make sure you use overdrive then powerfist, because sheen and powerfists abilities don't seem to stack. Luckily with blitzcranks super lower cooldowns, you can pretty much spam both while your masteries should keep you near full mana throughout the game. Use powerfist and static field to save your squishies from others.
With this build you won't really be a carry, as most games i play with this build have me around 5-10 kills, 0-3 deaths, and like 20 assists. I'm open to suggestions on the build because i'm pretty new to the super-competitive side of LoL but i find this build works pretty well for me. I've contemplated trying an extra manamune or sword of the occult (due to the low number of deaths you'll have, but you also don't get a lot of kills), but against tanks the black cleaver is pretty necessary. The other reason i didn't want another manamune is because i don't know what the max mana is (if at all). Thats also why i haven't chosen runes, but if this build isn't at max mana yet, i would get more mana, attack speed, attack damage and maybe a little mana regen. Like i said, i'll listen to any suggestions and i recommend trying the build before voting.