Depends on what you want from your epics! Each pool has highs (Force of Nature, Rise of the Phoenix, Snow Storm, EMP, LRM) and lows (Body Armour, Repulsion Field); but everything has utility. What do you want your blaster to do that he can't already? What does your blaster already do well at and want to improve further upon?
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Alvan made a great post about blasters epics here
On my Sonic/Mental(currently 45 say hi if you see a golden robot with a fro 
) blaster i first chose elec for another cone and the armor.
I later found the cone way to slow for my needs and i couldnt fit anywhere in my cone chain.
I then tried ice but didnt like it and didnt fit me in gameplay and thematically.
Now i´m going munitions and i like it so far, body armor is as Alvan says pretty meh but its nice to have some sort of defence.
Cryo Freeze Ray is a nice hold which will be awesome once i proc it out, you can slot both ranged sets and hold sets.Its also nice to hold some of the more pesky critters like sapper.
I cant wait until i get my missile and slot it.
** Cold **
Snow Storm - Slows opponents. Good for PvP duels (Slows, interrupts Aid Self).
Hibernate - "Phase Shift + Rest" Panic Button. Again, good for PvP.
Flash Freeze - Ranged Sleep. OK for soloing. Fairly useless on a standard team
Frozen Armor - Fairly low values for S/L Defense. Good for slotting a LOTG
** Electrical **
Static Discharge - Ranged Cone. Moderate Activation time and damage.
Shocking Bolt - Ranged Hold. Moderate activation time. Needs slotting to perma.
Charged Armor - Best Resistance Shield of all Blaster Epic pools. S/L/Energy.
EM Pulse - PBAoE Disorient. Long Activation time. Very Long Recharge. Death Magnet.
** Flame **
Bonfire - KnockBACK patch. Good for soloing or keeping mobs away from squishies.
Char - Like Shocking Bolt, but with a faster activation time and higher damage.
Fire Shield - Good Resistance shield. S/L/Fire/Cold
Rise of the Pheonix - Self-Rez, very high PBAoE damage + 10-secs of invunerability.
** Force **
Personal Force Field - High Def/Resists + "Only affecting self". Good Panic Button.
Repulsion Field - PBAoE Knockback toggle. Only take if you have a single-digit IQ.
Temp Invunerability - Mediocre Resistance Shield. S/L only. Nothing Special.
Force of Nature - 2 minutes of Godmode, no status protection or health crash.
** Munitions **
Body Armor - Auto Resistance buff. Very low S/L values. Good place for procs.
Cryo Freeze Ray - Ranged hold. Virtually no damage. Mediocre activation time.
Sleep Grenade - Same as Flash freeze, with better duration and activation time.
LRM Rocket - Unique Ranged interruptable "Snipe" Nuke. Long Recharge. S/L Damage.
Generally the PvP Pools are Force (for PFF and FoN) or Cold (For Snowstorm/Hibernate). PvE Pools can be anything, but you'll see a fair number of Fire (Rise of Pheonix + Char) and Munitions (for LRM Missile)... 
thanks for that guys,and thanks for that guide maelwys very helpful. I think i am going to take the force set i like the sound of force of nature(sounds like a light form copy) but in saying that i have just gained a vet respec if all goes bad
the hero formerly known as Mr.M
kin--d/blast lvl50 (retired)
'm reborn' lvl50 p/b(retired)
little miss psyche lvl50 ice/mm blaster on defiant
lil miss shade lvl50 warshade
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I'd recommend Force Mastery, as /Mental Manipulation synergises so well with it. Slotted you're looking at resistance cap to Smashing/Lethal, and very near resistance cap for everything else. Now, combine that with Drain Psyche's +Regen...
Manage to hit 107 hp/sec regen on my Fire/MM/Force Blaster with those resistances up, and I can assure you, you will not die while you are like that, so you can basically feel free to pop a breakfree and act like a Tanker with Blaster damage for the duration.
On top of that, when you feel FoN's about to crash, you have a nuke to fire off as well. You'll be end-crashing from it anyway, so no reason not to really, and it's a nice way to end your brief bout of invulnerability.
Just reached level 41,and i have a little question. Why doesn't anybody mention Electrical mastery's Surge of power?
By looking at the numbers,it's as good as Force of nature,and used in conjunction with the shield it could make you even more though,wouldn't it? Or am i missing something here?
Its an alright little power but I'd rather have slots for EMP and the Shield, I do have it but it's not overly slotted and I don't use it all that often, sometimes before a nuke because it gives me mitigation when I don't have endurance. Its more that Elec epic has better powers than it being a bad one
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But,what use is force mastery anyway? After all,one would take it protection and Force of nature......but you can take electrical mastery and have that,plus a shield,plus an hold....if one wants protection,it just seems to me that electricity beats force fair and square,where it should be quite the opposite
That is only recently. Old days only force had the ubah power along with PFF being permanent. The stupid knockback power also been lame, lousy and still is, only fun to use once in a while.
The post you reply is from august last year, back then there was no surge of power yet. Nowadays, elec is very very nice to take.
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PFF is useful in a pinch, and good for herding. Can also ghost through Rikti without problems with it on, in spite of Drones, and it's another place to slot an LotG: +Recharge.
Regarding the Hold in Charged Armour, it's a 2 second animation which I regard rather lengthy, so only worth it if you have a hold already to stack it with.
And there is a large difference between Force of Nature and Surge of Power. The former's crash is -100% recovery. The latter's is -10000%.
just about to ding 41 on my ice/mm blaster and i was wondering if there any must haves/must avoid power pools can be a bit of a minefield this choice. Any help would be appreciated
the hero formerly known as Mr.M
kin--d/blast lvl50 (retired)
'm reborn' lvl50 p/b(retired)
little miss psyche lvl50 ice/mm blaster on defiant
lil miss shade lvl50 warshade
GGRRR s/g member