Blitzcrank is a highly mobile support tank with a grab that can pull enemy champions from far away excellent for engaging team fights and pulling enemies out of their comfort zone

Since blitzcrank doesn't have to play aggressively due to his (rocket grab) ability you can use scaling runes I use scaling armor and magic resist runes with some armor quints
as a means of not being squishy in the start I also go full magic penetration runes because his r does a lot of damage mid game due to these magic penetration runes

marks- 9 magic penetration
seals- 9scaling armor
glyphs- 9 scaling magic resist
quints- 3 flat armor

I use 6/6/18 on blitzcrank

I like to use blitzcank as a tank due to his undisputed engaging power he must be able to tank damage and these masteries will allow him to do so

r>q>w>e

R-his most damaging ability
Q-his most useful ability
W-his utility
E-you really only need 1 point in this ability all its good for is a knock up get it at 3 then leave it alone till you have full points in all your other abilitys

pros
1.very strong engages
2.Dedicated tank with scaling runes and tank items
3.Has a great lane phase due to his ability to play passively and still be dangerous
4.R does great damage and has a very low cool-down
5.Excellent ambush potential
6.Is a champion that requires a skilled user to play effectively
Cons
1.very bad 1v1 potential
2.not a greatly damaging champ late game
3.Is a champion that requires a skilled user to play effectively
4.Can be counterd hard by other true tank supports such as Leona and Alistar

Blitzkrank works very well for engaging and ambushing when he rocket grabs an enemy Carrie into his team it ends badly for the enemy carrie 99.9% of the time

He is tanky which is great for absorbing very damaging spells most which would kill most carries he makes excellent peel for his carries

Blitzcrank has a unique ability to be able to pull an opponent over walls and virtually any terrain due to his Q (Rocket-Grab)ability is only as good as the imagination and skill of the user.

Use relic shield procs on large cannon minions while adc is in lane