Currently own:
3DS XL. Bought it nearly two years ago to play Monster Hunter 3 Ultimate, since the series was no longer developed for the PSP's. It's still perfectly usable, but its battery life is quite reduced now since it's used so often, and the 3D switch doesn't usually turn the 3D on, it just randomly decides to come on now and again randomly while I'm playing. Probably the best system I've had besides the GBA SP.
GBA SP. Bought it preowned about 3 and a half years ago to play the old Pokemon games (Fire Red and Ruby) and a couple of other games that I really enjoyed. Still seems to work perfectly fine, although I haven't used it in about a year since having the 3DS XL.
I used to own:
A GBA. This was the first console that was my own personal console, got it for Christmas when I was 6. Had a lot of joy with it, of course the lack of a backlight on it was a pain in the backside, so I ended up buying one of the little lights that attached to it. Kept it a while, but it got traded in and I got a GBA SP from my parents when it came out.
GBA SP. Got it on release after having the GBA traded in and had it as a Christmas present. Had it a couple of years, but it got traded in for the DS when it got released.
DS. The first console that I bought myself, along with a bit of financial help from the GBA SP. I remember being really excited by the touch screen, and for the system after trying Super Mario 64 DS with the demo in the GAME shop. I had several of them, one got damaged by falling out my pocket when it fell down the stairs and the screen shattered, and another had the connection between the two screens get damaged. I liked some of the games on the system, but the one I was looking forward to was Pokemon, and IIRC Pearl and Diamond kept getting their release pushed further into the future, so in the end my 12 year old self got impatient and traded it in since by this point I had a PSP which I played far more often. I got about ?60 for my entire collection of DS and GBA games(Which included about 40 GBA games and 15 DS games) and DS, looking back I kind of regret it, as quite a few of the GBA games are worth a small fortune now if they're legitimate copies and I got between ?0.20-1.00 per game. Of course, shortly after I traded it in, Pokemon Pearl/Diamond came out, still haven't tried them to this day.
Gamecube. Think my brothers and I got this on Christmas 2005, came with Mario Kart Double Dash. We had Sonic Adventure 2:Battle as well when we received it, as well as another game which was rubbish. Never was very impressed with it, especially as the data on the memory cards kept getting corrupted, so it got traded in after a year or two.