Can't go wrong with Fire/Fire.
Ice/Energy is still probably the strongest of the conventional builds for PvP/soloing/single target plus very good survivability in teams including sub-standard ones.
Elec/En and Elec/Elec are both very popular, although I think having played in Ice/Energy if you blapped with it you would probably find either of those combinations a little dissapointing as they're similar, but not quite as good in a lot of respects.
For PvE builds Fire/Ice is a very nice combination you don't see used much, although tight on endurance it's good for teaming and good for soloing. Shiver and Ice Patch both really help the survivability of a high damage AOE primary, I've been really impressed with this combination.
Fire/Energy is also very good, Fire/Elec is OK if you wanted to try something that didn't give you a secondary you'd already used. The Fire Primary in general is very strong for PvE, adding a secondary that gives you a good measure of survivability really helps.
Ice/Ice/Cold is great for a high control build, plays quite differently to Ice/Energy as well so might not feel too much like you'd "done it all before" so to speak. Ice/Ice is nice for a PvP build that's a little different from the norm as well. Works pretty well against certain character types that give your more standard blapping builds a hard time.
Energy Blast I have no real experience of other than the annoyance of teaming with bad ones, knockback drives me nuts, I always delete them before they get to level 20.
Sonic, again, I haven't played, but for teaming I like the set overall. My only concern is a lot of the long animation times. Teaming with one is fun though, lots of damage and boost to team damage from the -res. I teamed quite a bit with a Sonic/Energy Blaster a while back and was really impressed with what he did with the build.
Bleh, there's lots of fun ones out there.
I'd go for avoiding Archery and AR from the primaries. I wouldn't advise Elec with anything other than Elec or Energy secondary, as you'll get no milage at all out of end drain, without that you might as well take something that does more damage.
From the secondaries Fire is still not fantastic for survivability, although if you took a high control primary you could make it work, it always feels a little messy. If you really wanted AOE damage I'd just take the Fire Primary which has more than enough AOE capability, and add a secondary to support it. I'd also avoid devices secondary unless you're building to PvP and/or solo a lot, in which case with certain primaries it can be very good. In a team situation with /devices, you just end up getting outdamaged by the blaster with aim and build up who's doing more front loaded damage. Electricity Manipulation while quite good, has little that Energy doesn't do better, although Elec does look a lot cooler. 
fire/fire is immense fun and with a good team you will be destroying all before you with aoe goodness.
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I love my Blasters too and Fire/Energy is a good combination. A little more control than Fire/Fire and good for opening with impressive AoEs and then finishing off with single-target blapping. Once past SO level the damage you can do is awesome. Large spawns are a joy as they all fall down at once.
However, Sonic/Energy is still my favourite. The sheer amount of control you can apply to a situation is great and if you're with a team that understand soft controls like Knockback, Disorient and Sleep, you can be tremendously useful. This is even before you take into consideration the -Res that's already been mentioned in the blasts. The only downside is that you will be single-target focused so it can be easy to become overwhelmed if solo but then that's when the control powers come in most useful. The animations are a little 'rooted' but still not as bad as say 'Flares' from Fire Blast so I believe that they're liveable with. I've heard that the Nuke is one of the best in the game as well as it disorients anything that survives so the end crash might well be survivable. I'll find out in two levels time.
Good luck in choosing, being a Blaster is like being a gun and the joy is in pulling the trigger.
@Dante EU - Union Roleplayer and Altisis Victim
The Militia: Union RP Supergroup - www.themilitia.org.uk
Energy/Energy are the most fun you can have with your clothes on.
Well, Almost 
My favo nowadays is AR/Ice. Weird set, annoyingly set sometimes, but i so love the aoe power in the AR set (i never tested, but i wonder if it can beat fire aoe power - maybe AR/fire would). Teamwise its even more awsome to play with, solo is pretty slower then sets like Ice-sonic-elec/nrg although fun to play.
For double exp, dont solo this build, in team.. it beats my Ice/nrg anyday.
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If you're gonna team fire/fire ftw. Although there are some players out there who will not team with you - these people are ignorant and unworthy to be allowed to hold the star. A good fire/fire blaster is always worth a slot in any large team. Don't shy away from letting off Fireball and firebreath as often as possible but remember this; Buff as much as possible and let others aggro first, acrobatics is your friend and inferno will make you smile every time 
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The Energy/Energy combination is the most fun you can have with your GR1SM battle suit on.
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Edited to remove any possible Speedo contamination and prevent unnecessary mindbleach releases.
Is it time for the dance of joy yet?
Having not played the game for about 4 months, and my AT love being blasters (however hard I try to escape this!), I've been considering leveling a new one, using Double XP weekend for a boost, as well as all the other stuff that'll no doubt be going on. My question is, what's regarded as effective these days? What's popular and why? Any unorthodox combinations that people are loving?
). So yeah, any thoughts would be appreciated.
Bear in mind I have a level 50 Ice/Energy which I was playing for over a year (It took me that long to level it with regular playing... go me