I spent some time and got these results, I'll explain each one a little bit.
1. Walking War Robots
A online multiplayer based game, the download is 186 MB, but you can jump right into it from the start (with the help of a tutorial). You get a mech that looks like a crab (with missiles and a machine gun in the arms. you can upgrade and unlock new weapons, and of course, there's premium stuff too like some games, but you can still get most of everything over time. Odd thing is, all the matches I go into so far (5 matches so far) have incompetent players and one competent player (I think the incompetent are bots, but I could be wrong)
2. Metal Wars (series of 1,2,3. 3 is the link)
"If you've played Armored Core or Chrome hounds before, this has the same formula" (quoted from a review)
While I've seen this app a few years back, it didn't click as I just passed it. This is one of those rare mech games that are both good and bad, but better than the rest. Graphics, customization, and a storyline prove somewhat interesting. However, being a arcade, I believe it lacks a multiplayer, but for a game with it's graphics and customization should keep you interested in playing. Oh, and it's $1.99, figures

3. Protomech
Heh, as the name of it is irony, this game isn't or rather, doesn't feel finished. What I can say though is that with graphics similar to that of Mechwarrior 2, and with average controls and silly giant mech bosses at the end of each level, you can blow off a little steam and kill those meta players like you mean it! (well you can imagine, but hey, imagination's is mans greatest thing, right? *cough battletech cough*

Well that's a few I've found to be noticeable in either graphics, mechanics, or in detail.
If you have some games that fall into this category, postem! No, not those emulated games silly

And mind you, these are for you when you're not home or waiting for your group in the game to be ready or even CW, or, to blow some steam off or try something new.