Ok, let's see. I'm mostly aliens, although I usually join randomly. Seems like marines are always stacked...
As a vanilla skulk I'm average at best. With cloaking I'm good, silence helps a little. My favourites are cloaking - silence - regen, obviously. At three hives, my well-placed xeno-leaps become rather deadly though, but I'm rarely skulk by that point.
Gorging. I had a period where I would almost always permagorge. After placing my rt, I'd go "Hey, I've got 5 res, that's only 10 res away from another rt. I'll wait until I've placed that one as well" etc., so I've had a bit of training as a Gorge. One-on-one with a vanilla marine I'm usually dead meat, unless I have an rt to take cover behind, in which case my chances are at least 50-50. One of my favourites is placing two OCs beside each other, blocking off a hallway. Marine will see me behind the OCs and jump over to take me out. The problem is that I simply time my jump with his, and we end up in the same situation as before, just on opposite sides of the wall. He rarely lives to jump back.
Lerk. I love the Lerk. I need regeneration, but as soon as I have it I'm a pest. I know what kills a Lerk, and I dilligently steer clear of such situations, although a marine with good aim can sometimes surprise me and kill me anyway. Otherwise, the spore - spike combo is unbeatable. I'll spore 'em and make 'em chase me until they have to reload, then finish 'em off with spikes. Some maps are better suited to this than others. Origin is Godsent. I stay clear of marine spawn, focusing on killing the rines in the field instead. The rfk is mad.
Fade. I make a decent Fade. Not a really good one, but a decent one. I'll usually focus on taking the nodes down, an approach that tends to work well, but I can hold my own against vanilla rines as well. Shotguns and hmgs give me trouble, often to the point where I'll rather just go and do damage somewhere else than risk death.
Onos. Yeah bay-bee! Who doesn't love the Onos? Oh wait... Well, I do. I focus on staying alive, THEN on doing damage. As an Onos I'm slow, and a rush can kill me if I'm low on health and stamina, I know this. Staying alive is my number one priority until we get at least two more Onos up and running, which is what I call "critical mass", the point where we just run rampant through the map.
My biggest weakness as an alien is being fed up with my team, or deciding that I've done enough for them. At some point I'll simply go "Ok, I've built enough stuff for the team, time to reswhore!" And sometimes when my team is being particularly n00bish (im my opinion) I'll just go and sit in a vent and sulk. Usually when we have one hive and all of their team is outfitted in Heavy Armor. Seems like nobody takes down the rts if I don't... So much for going Lerk. *grumble*
As a marine, I manage to get by. My aim has now reached a point where skulks in the open rarely kill me. Once they get up close I have serious problems though, and usually die. I like Heavy Armor (who doesn't?), and can do decently well with a JP depending on the map.
HMG: I love it, what more can I say?
Shotgun: VERY mixed feelings. I like the one-hit-wonder that it is, but I dislike that I have to let the enemy get close first: My high ping means that I'll usually kill skulks in one blast up close, then get bitten a fraction of a second later. As a heavy this isn't much of a problem, but as a vanilla rine I don't do too well with the shotgun. And I hate dying with equipment.
GL: I tend to get direct hits from time to time (and managed to kill a fleeing Onos at least once), but usually I'll just stay in the background and spam the battlefield in front of me when the fighting starts.
My biggest weakness is probably taking orders. Unless the commander is very tight and I'm 100% sure that he is 100% sure of what he's doing, I'll try to "interpret" orders given to me, which sometimes leads to me not doing what the commander wants me to do. Sometimes it pays off, sometimes I screw up.
