General

A mega venusaur would rip your team to shreds. Thick fat ability, Sleep powder + leech seed.

[quote=tonytony40]I usually try to build around my favorite core:
Gastrodon-Heatran-Skarmory
This defensive core is extremely difficult to beat, as it the members have great coverage for each other.
Gastro with storm drain covers Heatran's fear of water types, and Skarmory's flying type covers Heatran's fear of earthquakes.
Both heatran and skarmory are extremely capable of tanking hits from Gastrodon's only weakness- grass.
Skarmory's fear of fire is negated by Gastrodon's typing and Heatran's ability, flash fire. It's fear of electricity is also negated by Gastrodon's typing.

Overall, the type coverage with this core is extremely effective and frustrating to play against.[/quote]

But skarmory (assuming you do entry hazard set) and gastro are not the best in terms of offense so it can allow for the opponent to do some nasty set ups.
EDIT: if you are running roar or whirlwind then it really depends on what pokemon the other guy is using but yeah overall its a pretty nice combo

The main problem the lack of a defensive core as someone said previously. Usually I like to use a triple core revolving one physical defensive wall and one specially defensive wall. Both pokemon should be able to cover each other's weaknesses. I prefer the last pokemon in the core to be a more offensive threat that can act as a more neutral switch in for certain pokemon that can heavily damage both walls. Currently, I am using a defensive gliscor and sp.def ferrothorn with a defensive reuniclus. Gliscor and Ferrothorn have very good synergy. Ferrothorn can take the attacks that gliscor cant and vice versa. Reuniclus is the neutral switch-in to threats if you are forced into a situation where a certain pokemon's movepool can severely damage any of your walls.
Most importantly is the revenge killer, I personally prefer ditto as the choice scarf revenge killer. Ditto in particular is probably one of the most powerful revenge killers in the game. It will easily outspeed the opponents pokemon and will pose an immediate threat.
Also, stealth rocks

TL;DR- Defensive Core, Revenge killer Ditto, Stealth Rocks

I usually try to build around my favorite core:
Gastrodon-Heatran-Skarmory
This defensive core is extremely difficult to beat, as it the members have great coverage for each other.
Gastro with storm drain covers Heatran's fear of water types, and Skarmory's flying type covers Heatran's fear of earthquakes.
Both heatran and skarmory are extremely capable of tanking hits from Gastrodon's only weakness- grass.
Skarmory's fear of fire is negated by Gastrodon's typing and Heatran's ability, flash fire. It's fear of electricity is also negated by Gastrodon's typing.

Overall, the type coverage with this core is extremely effective and frustrating to play against.

[quote=TheMo]Would the team of
Gengar
Houndoom
Salamence
Medicham
Blastoise
? (Dont know what to put here) be a good online team? Thanks![/quote]

Houndoom is just an ok pokemon statistically but the abundance of water, fighting, and now fairy types basically nullify Houndoom.
Gengar is a great pokemon especially with mega evo but its one huge weakness is sucker punch.
Salamence another solid choice not much to say here except watch out for fairy
Medicham is a very good poke with mega evo but without mega evo just dont use it ... ever. You probably know this but you can only have one mega evo so I am assuming medicham is it.
Blastoise is just plain outclassed in terms of speed and movepool. There are much better water pokemon like jellicent (which also has amazing tanking skills) tentacruel for spikes and rapid spin plus decent offense or even politoed for rain.

My tip: Get a strategical/ playmaker poke like sableye for example. It can priority willo wisp and even do item swaps. An entry hazard pokemon would also be good as stealthrock can cripple many pokemon (ie volcarona)

you need a rock or ground type

@TheMo: Yeah...that's the only one it learns.

[quote=yoguy911]@TheMo: maybe an azumarill, it's a fairy and has a priority that you're missing.[/quote]

U mean like aqua jet?

@TheMo: maybe an azumarill, it's a fairy and has a priority that you're missing.

[quote=yoguy911]@TheMo: not bad, but make sure to have it with an air balloon and have your houndoom have flashfire.[/quote]
Thanks, any suggestion for a 6th pokemon?

@TheMo: not bad, but make sure to have it with an air balloon and have your houndoom have flashfire.

[quote=yoguy911]@TheMo: mega gengar is OP, but most people have counters for it (sucker punch) so it might not be the best option. i heard mega medicham is really good, but there are better megas out there. your team really need to have some priorities, and a fairy type that can counter dragons.[/quote]

Hows aegislash instead of gengar?

@TheMo: mega gengar is OP, but most people have counters for it (sucker punch) so it might not be the best option. i heard mega medicham is really good, but there are better megas out there. your team really need to have some priorities, and a fairy type that can counter dragons.

[quote=HolyDragon]I don't understand how this team is bad. Then again, I've always just chosen pokemon team based on looks and made sure to diversify types.[/quote]

I chose these pokemons because they covered each others weakness, as a whole they are only weak to rock ground and ghost

I don't understand how this team is bad. Then again, I've always just chosen pokemon team based on looks and made sure to diversify types.

[quote=yoguy911]which is your mega?[/quote]

This is just a thought it be either gengar or medicham i would use

I can destroy you with my Alakazam alone.

which is your mega?

nope they will own you

A wise man once told me: Any team can be a good team, but the same team can be a bad team.

no thats a terrible team