Rocket Jump + Disintegrate is amazing.
Also Rocket Jump plus his push ability wins games when teamed with Ambuscade.
For defense, definitely get his Adaptive Subroutine. An extra miss chance is huge in this game. Especially if someone aims at you and you have 6 as an auto-miss. Since you can't dodge, others aiming at you is a big weakness. Remember, too, that melee attacks will miss on 1's against you due to the reach penalty. So, in essence, you can give those Lightspeed Barrage attacks 3 numbers they miss on. 1, 2, and whatever your auto-miss is. Grenade Launcher would miss on similar values.
Omnitron V's strengths are his battlefield control, his mobility (ironically!, thanks to Rocket Jump), and his devastating disintigrate. Team him up with other heroes who can tank for him if the enemy has characters like Bunker, Wraith, or Tachyon (Legacy or Citizen Dawn with Citizen Truth work well for this), give him defensive capabilities (like Unity with Stealth Bot or Visionary with Foresight and Twist the Ether) or with people who need someone with amazing battlefield control (AZ, Ra, Unity, Operative, Ambuscade). A push of 2 through one or more hazard spaces can take down most opponents. Remember that each movement of the push, if into a hazard space, triggers that hazard space's attack. If Ra uses Living Pyre and Blazing Tornado to generate 2 hazard spaces and Omnitron V pushes someone through them, that's 4 attacks against that person. And Omnitron V can push all enemy charactes within 2 hexes of him. This is the strongest push in the game.
Let's look at Omnitron V's abilities:
1. Immense Frame: This gives Omnitron V 3 bonuses and 2 penalties. First, the elevation change is a bonus, as it allows him to hit enemies at higher elevations easier and it makes melee heroes have one more miss value against him. Second, Omnitron V has mobility. This one is obvious and a bit necessary with his base move speed. Third, he is immune to push. This is HUGE! He cannot be affected by most hazard space strategies against his own will. I think the only one that still works is Kusarigama from the Operative, since it moves the target instead of pushing it.
2. Omni-components: Also very strong. Usually Tactics Sequence is chosen for this one, as it gives him an extra action and reduces his penalties to himself for being elevation 1.
3. Rocket Stomp: A melee attack for 4 dice. Pretty average. And its miss numbers pretty much already take his own elevation difference into account.
4. Adaptive Subroutine: Give the enemies an extra miss chance. In this game, miss-chance is where half your character's defense lies. If the enemy rolls dice that hit that miss number, they can't be used for aim! This is huge!
5. Disintigration Cone: 6 dice, origin 0. It ignores your own elevation penalty issue since it is a vertex attack. It is Omnitron V's strongest attack and works really well when aimed.
6. Interpolation Field: Already mentioned. This is the strongest push in the game. Amazing.
7. Ocular Beams: Attack 2 targets, 5 dice, lots of miss chances. It is a pretty good attack, since the miss chances are low numbers, and hitting two targets is nothing to scoff at. Also, both attacks are ranged, allowing Omitron V to use up to two ranged attacks in one turn when combined with Remote Tranquilizer. Since Remote Tranquilizer is an area attack, that allows him to attack 2 characters that are close together twice in one turn. Pretty nice!
8. Remote Tranquilizer: Area attack, radius 1. 4 dice. This attack is amazing if it hits, since it debilitates the enemy. Works well against anyone who likes to build up tokens (we're looking at you, Bunker, Legacy, Wraith, Ra and Ambuscade!). It also allows Omnitron V to hit people in cover, as long as the origin of the attack is outside of that cover.
9. Rocket Jump: This ability gives Omnitron V the mobility his dice rolls don't. Since he chooses one part of himself to move, then can rotate around it, this is equivalent to moving 5 hexes in one move. He can close distance fast and follow up with a disintegration attack or an interpolation field to distrupt any enemy lineup. Don't forget that you can use this to run away as well. The defense -1 token is pretty bad, but the Adaptive Subroutine counterbalances it very well.
10. Tactics Sequence: This and Adaptive Subroutine will be the most common abilites for Omnitron V to use. Extra actions are amazing. What reduces its effectiveness is the fact that Omnitron V can't sprint or dodge. Use this ability when you plan on moving in to give you an aim action before you attack. Rocket Jump + Aim + Disintegrate makes someone cry.
Heroes Omnitron V is strong against: Citizen Dawn (knock her and Citizen Truth away from each other), Unity (Stealth Bot can't stealth allies that aren't nearby!), Proletariat (multiple attacks that hit multiple targets! Imagine a Remote Tranquilizer that hits more than one Proletariat!).
Heroes Omnitron V is weak against: Bunker (lots of attacks, free aim), Wraith (free aim, can slip into shadows to avoid retaliation), Proletariat (more Omnitron V to be surrounded and smacked, plus the push actually works against you here!), Ambuscade (he likes to pop up and attack with an aimed Custom Hand Cannon! Ouch!).
Note that he is both strong and weak against Proletariat. Omnitron V leads a confused life. Probably comes from being cobbled together for the fourth time in his existance. A photocopy of a photocopy, etc.