This page is about the new megas that were introduced in Pokémon Omega Ruby and Pokémon Alpha Sapphire (A.k.a ORAS) 

Gen 1 megas added in ORAS:

Mega Beedrill

This is mega-Beedrill

Ok let's face it Beedrill is pretty bad, that is what gamefreak must have thought when they made this mega. Mega Beedrill is a bug-Poison type and gets a huge boosts to its attack and speed stat. Mega Beedrill gets the ability Adaptability, that will boost the Same Type Attack bonus (STAB) of beedrills Bug and Poison type moves.

Mega Beedrill's stats: 65 HP/ 150 Atk/ 40 Def/ 15 SpA/ 80 SpD/ 145 Spe

Mega Pidgeot

This is mega pidgeot

Mega Pidgeot is a Normal-Flying type with the abllity No Guard, Because of this ability moves used by or on this Pokémon will never miss, that can be good or bad of course cause thunder will also never miss. Mega Pidgeot gains huge boosts to his speed and special attack just for setting the hurricans

Mega Pidgeot's stats: 83 HP/ 80 Atk/ 80 Def/ 135 SpA/ 80 SpD/ 121 Spe

Mega Slowbro

This is Mega Slowbro

When this new 'mega' got revield nobody was exited even if it was a mega that nobody expected. Everybody thought it was way too weak but to be fair he is not he is a tanking wall and perfect for stalling. Mega Slowbro is a Water-Psychic type with the ability shell armor. Due to shell armor you cannot crit this Pokémon and that makes it an ever bigger stalling wall. 

Mega Slowbro's stats: 95 HP/ 75 Atk/ 180 Def/ 130 SpA/ 80 SpD/ 30 Spe

Gen 2 Megas added in ORAS:

Mega Steelix

This is Mega Steelix

Mega Steelix is a Steel-Ground type with the ability Sand Force. Due to Sand Force, Mega Steelix his Ground, Rock and Steel type moves get bossted in a sandstorm. Mega Steelix gains (just like mega Aggron) a huge boosts to his Defence but instead of being defence wall he is a Bulky attacker. That is because his Attack also gets a huge boost

Mega Steelix's stats: 75 HP/ 125 Atk/ 230 Def/ 55 SpA/ 95 SpD/ 30 Spe

Gen 3 Megas added in ORAS:

Mega Sceptile

this is Mega Sceptile

Mega Sceptile is a Grass-Dragon type with the abillity Lightingrod. Lightinrod turns electric type attacks in more SpA. Many people think this is a wierd ability cause Mega-sceptile already resists electric 4 times. The reason behind this is that you cannot paralyse Sceptile with thunder wave anymore, so his high speed stat stays high. You can still paralyse mega Sceptile with the move glare though.

Mega Sceptile's stats: 70 HP/ 110 Atk/ 75 Def/ 145 SpA/ 85 SpD/ 145 Spe

Mega Swampert

This is Mega Swampert

Mega Swampert is a Water-Ground type with the ability Swift Swim. Swift Swim doubles Mega Swamperts speed stat if it is raining. Because his speed stat is already boosted by the mega evolution this is a good ability for rain teams. Mega Swampert got also a big boost to his attack and changed the meme 'i herd you liek mudkiepz' into 'i herd you liek Murder'.

Mega Swampert's stats: 100 HP/ 150 Atk/ 110 Def/ 95 SpA/ 110 SpD/ 70 Spe

Mega Sableye

This is Mega Sableye

Mega Sableye is a Dark-Ghost type with the ability Magic Bounce. Because of Magic Bounce every status move is gone be bounced back at the opponent. Because the reason that you cannot toxic this thing and his increased defences, this Pokémon is an annoyer. But when this pokémo got revielt people thought it would be a really bad mega cause it didn't had Sableye's normal ability prankster. That is the reason people nowadays first use prankster to their advantage and then mega evolve.

Mega Sableye's stats: 50 HP/ 85 Atk/ 125 Def/ 85 SpA/ 115 SpD/ 20 Spe